Digital SAT: Main Idea 3

1. In the early study of ocean currents, scientists often focused on surface movement that could be observed from ships, such as the paths of drifting objects or the direction of floating seaweed. Later researchers developed instruments that measured temperature, salinity, and pressure at different depths. These measurements showed that deep ocean currents, though invisible from the surface, play an important role in moving heat and nutrients around the planet. As a result, scientists came to understand ocean circulation as a complex system extending far below the water’s surface.

Which choice best states the main idea of the text?

A) Early scientists were unable to study ocean currents because they lacked instruments that could measure surface movement.

B) New ways of measuring conditions below the ocean’s surface expanded scientists’ understanding of ocean circulation.

C) Deep ocean currents are more important than surface currents because they move heat and nutrients around the planet.

D) Scientists now believe that floating objects and seaweed provide no useful information about ocean movement.

2. For many years, researchers studying animal migration focused mainly on the physical abilities that allowed animals to travel long distances, such as wing strength in birds or endurance in fish. More recent studies, however, have examined how migrating animals use environmental signals, including Earth’s magnetic field, the position of the sun, and changes in water temperature. These findings suggest that migration depends not only on animals’ capacity for movement but also on their ability to detect and respond to cues in their surroundings.

Which choice best states the main idea of the text?

A) Researchers have found that birds and fish rely on the same environmental signals when migrating.

B) Animal migration is less physically demanding than scientists once believed.

C) Scientists now believe that Earth’s magnetic field is the only reliable guide used by migrating animals.

D) Recent research has broadened scientists’ understanding of migration by showing the importance of environmental cues.

3. For many years, scholars studying maps from the Age of Exploration focused mainly on their geographic accuracy, noting where coastlines, islands, or inland regions were drawn incorrectly. More recently, historians have examined the decorative elements on these maps, including ships, sea monsters, flags, and portraits of rulers. These details often reflected political ambitions, trade interests, and cultural assumptions about unfamiliar places. This newer research has shown that old maps were not only attempts to represent geography but also expressions of the ideas and priorities of the societies that produced them.

Which choice best states the main idea of the text?

A) Historians have expanded their study of old maps by considering what their decorative details reveal about the societies that made them.

B) Maps from the Age of Exploration became less accurate when artists added ships, sea monsters, and portraits to them.

C) Scholars now believe that the decorative elements on old maps are more useful than the geographic information they contain.

D) Political leaders used maps mainly to correct misunderstandings about coastlines, islands, and inland regions.

4. For many years, researchers studying ancient theater focused primarily on surviving scripts, analyzing dialogue, plot, and themes to understand how plays were written. However, scripts reveal only part of what audiences experienced. More recently, scholars have examined theater architecture, masks, costumes, and references to music and movement. This evidence has helped researchers better understand ancient theater as a performance tradition shaped not only by words on a page but also by sound, space, and visual design.

Which choice best describes the overall structure of the text?

A) It compares two ancient plays, explains why one was more popular with audiences, and then identifies features they shared.

B) It argues that surviving scripts are unreliable and proposes that scholars should stop using them as evidence.

C) It describes several types of theater architecture and explains how each affected the themes of ancient plays.

D) It presents an older scholarly focus, notes a limitation of that focus, and introduces additional evidence that has broadened scholars’ understanding.

5. In the early study of volcanoes, scientists often focused on eruptions themselves, documenting lava flows, ash clouds, and the damage caused by explosions. Later researchers began examining the quieter periods between eruptions, measuring small earthquakes, gas emissions, and subtle changes in the shape of a volcano’s surface. These observations showed that volcanoes can reveal important signs of internal activity long before an eruption occurs, allowing scientists to better understand and monitor volcanic behavior.

Which choice best states the main idea of the text?

A) Volcanic eruptions are easier to predict when scientists study the damage caused by past lava flows.

B) Scientists have improved their understanding of volcanoes by studying signs of activity that occur between eruptions.

C) Small earthquakes near volcanoes are usually more dangerous than ash clouds or lava flows.

D) Early volcano research was inaccurate because scientists ignored the role of gas emissions.

6. For many years, researchers studying ancient roads focused mainly on their military uses, especially how they allowed armies to move quickly across large territories. More recent studies, however, have examined roadside markets, inns, and repair stations found along these routes. This evidence suggests that roads also supported regular commercial activity and social exchange, connecting small communities as well as major political centers.

Which choice best states the main idea of the text?

A) Ancient roads were originally built for trade but were later adapted for military use.

B) Researchers have found that roadside markets were more common than military stations along ancient roads.

C) New evidence has broadened scholars’ understanding of ancient roads by showing that they served commercial and social purposes as well as military ones.

D) Ancient communities depended on roads mainly because local markets could not survive without travelers from political centers.

7. For many years, historians studying medieval towns focused mainly on official documents such as charters, tax records, and court rulings. These sources revealed important information about laws and institutions, but they often said little about how ordinary residents experienced town life. More recently, researchers have examined objects found in wells, trash pits, and abandoned houses, including broken pottery, tools, and food remains. Such evidence has helped historians understand daily routines, household work, and patterns of consumption that written records alone rarely captured.

Which choice best states the main idea of the text?

A) Medieval town governments kept official records mainly to document the daily routines of ordinary residents.

B) Archaeological evidence has helped historians develop a fuller picture of everyday life in medieval towns.

C) Historians now believe that charters and court rulings are too unreliable to be useful for studying medieval towns.

D) Broken pottery and food remains show that medieval towns were less organized than historians once believed.

8. For many years, researchers studying early printing focused mainly on the books produced by famous presses, especially large religious, legal, and scholarly works. More recently, historians have examined cheaper printed materials such as pamphlets, calendars, song sheets, and advertisements. Though these items were often discarded after use, surviving examples show that printing affected everyday communication as well as formal learning. This broader evidence has helped scholars understand early print culture as part of daily life, not just as a tool for preserving important texts.

Which choice best states the main idea of the text?

A) Studying inexpensive printed materials has expanded historians’ understanding of how early printing shaped everyday life.

B) Early printers were more successful when they produced pamphlets and calendars than when they printed religious or legal books.

C) Historians now believe that famous presses were unimportant because most people preferred advertisements and song sheets.

D) Cheap printed materials were usually preserved more carefully than large scholarly works because they were used more often.

9. For many years, scientists studying bird nests focused mainly on their shapes and building materials, classifying nests as cups, platforms, burrows, or cavities. Later researchers began examining where birds placed their nests and how those locations affected survival. They found that factors such as shade, height above ground, and distance from predators could be just as important as the nest’s structure itself. This work has encouraged scientists to understand nest-building as a set of choices shaped by both construction and environment.

Which choice best describes the overall structure of the text?

A) It compares several bird species and explains why some build more complex nests than others.

B) It argues that nest shape is no longer useful for classifying bird behavior and should be replaced by location data.

C) It describes an initial research focus, introduces an additional factor researchers began studying, and explains how that factor broadened scientific understanding.

D) It presents a problem birds face when building nests and then lists several unsuccessful ways they try to solve it.

10. For many years, historians studying public clocks in medieval and early modern cities focused mainly on their mechanical design, such as the gears, weights, and bells that allowed them to keep and announce time. More recently, scholars have examined where these clocks were installed and how city residents used them. Public clocks placed on towers, churches, or town halls helped coordinate markets, work schedules, religious observances, and civic meetings. This research has shown that public clocks were not only technological achievements but also tools that helped organize urban life.

Which choice best states the main idea of the text?

A) Public clocks in medieval and early modern cities were usually installed in churches because religious leaders controlled urban schedules.

B) Scholars have expanded their understanding of public clocks by studying their social role as well as their mechanical design.

C) The mechanical design of early public clocks was less important than the locations where the clocks were installed.

D) Public clocks became common only after city residents demanded more accurate market and work schedules.