What's the Main Idea?
The Great Wall of China was originally built by ancient emperors to protect their territory from invading northern armies. Construction workers used local stone, brick, and packed earth to create this massive barrier that stretched across thousands of miles.
What is the main idea of this passage?
A. Invading northern armies were very dangerous in ancient history.
B. Ancient workers used bricks and stone to construct buildings.
C. The Great Wall of China was built as a massive barrier to protect the country from invaders.
D. The Great Wall stretches across thousands of miles of sandy desert.
C. The Great Wall of China was built as a massive barrier to protect the country from invaders.
The Venus flytrap is a unique predatory plant that survives in poor soil by trapping and digesting insects. When an unsuspecting bug crawls onto its modified leaves and touches the tiny trigger hairs, the trap snaps shut in less than a second. Special enzymes then break down the insect, providing the plant with the essential nutrients it cannot get from the ground.
What is the main idea of this passage?
A. Tiny trigger hairs cause the Venus flytrap to snap shut very quickly.
B. The Venus flytrap captures and digests insects to get nutrients it needs to survive.
C. Insects like to crawl onto the leaves of unique predatory plants.
D. Venus flytraps grow best in rich, healthy soil deep underground.
B. The Venus flytrap captures and digests insects to get nutrients it needs to survive.
Mars appears bright red in the night sky because its surface is covered in a thick layer of iron oxide, commonly known as rust. Strong desert winds blow this rusty dust into the thin atmosphere, creating a permanent reddish haze around the entire planet.
What is the main idea of this passage?
A. Strong desert winds regularly blow dust storms across Mars.
B. Mars has a reddish appearance because its surface and atmosphere are filled with rusty dust.
C. Iron oxide is a chemical compound commonly referred to as rust.
D. Mars has a very thin atmosphere compared to the planet Earth.