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Main Idea and Its Support is a free printable Grade 4 English worksheet on working out a main idea from the details that support it, aligned to Common Core standard RI.4.2. It prints 8 questions with an answer key on its own sheet of paper, in 25 versions that each ask different questions, so no two students in the class work from the same page. Print it from the browser or download it as a PDF — no account, no email.

Set 7 of 25 · the same problems every time you open this link.

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Set 1 has all 25 in a single PDF. All 25 sets ask different questions.

Main Idea and Its Support

RI.4.2

NameDate

Circle the right answer.

1.A paragraph says: earthworms tunnel through soil and let air in; they drag dead leaves underground; their waste makes the soil richer. What is its main idea?
  • A.Leaves fall in the fall.
  • B.Earthworms live underground.
  • C.Earthworms help keep soil healthy.
2.A paragraph says: Arctic foxes grow a thick white coat in winter; their small ears lose little heat; fur on their paws stops them slipping. What is its main idea?
  • A.Ice is slippery.
  • B.Arctic foxes are white.
  • C.Arctic foxes are suited to the cold.
3.A paragraph says: Fleming saw mold kill germs; Florey and Chain found a way to make it in large amounts; by 1944 it was treating soldiers. What is its main idea?
  • A.Soldiers were wounded in 1944.
  • B.Mold grows in dishes.
  • C.Making penicillin into a medicine took the work of many people.
4.A paragraph says: plastic bags take hundreds of years to break down; turtles mistake them for jellyfish; many towns now charge for bags. What is its main idea?
  • A.Plastic bags harm the natural world.
  • B.Stores sell bags.
  • C.Turtles eat jellyfish.
5.A paragraph says: coral reefs cover a tiny part of the sea floor; a quarter of all sea creatures live on them; many fish lay their eggs there. What is its main idea?
  • A.Coral reefs are very small.
  • B.Coral reefs are home to a great deal of sea life.
  • C.Fish lay eggs.
6.A paragraph says: beavers fell trees with their teeth; they build dams of sticks and mud; their ponds give homes to fish and birds. What is its main idea?
  • A.Beavers change the places where they live.
  • B.Beavers have sharp teeth.
  • C.Fish live in ponds.
7.A paragraph says: Roman roads ran straight for miles; they were laid in layers so water drained away; some are still used today. What is its main idea?
  • A.Water drains away.
  • B.Romans liked straight lines.
  • C.Roman roads were built to last.
8.A paragraph says: lighthouses warn ships away from rocks; each one flashes its own pattern; sailors use the pattern to tell where they are. What is its main idea?
  • A.Lighthouses keep ships safe and help them find their way.
  • B.Lights can flash.
  • C.Rocks are dangerous.

LessonPrint · RI.4.2 · Set 7 · free to copy for classroom use

Answer key — Main Idea and Its Support

Set 7. Prints on its own sheet.

  1. 1.Earthworms help keep soil healthy.
  2. 2.Arctic foxes are suited to the cold.
  3. 3.Making penicillin into a medicine took the work of many people.
  4. 4.Plastic bags harm the natural world.
  5. 5.Coral reefs are home to a great deal of sea life.
  6. 6.Beavers change the places where they live.
  7. 7.Roman roads were built to last.
  8. 8.Lighthouses keep ships safe and help them find their way.

More practice for RI.4.2

State the main idea, show the details behind it, and summarize.

Teaching this next? The Main Idea and a Summary is the 40-minute plan for it, with the misconceptions to expect.

All Grade 4 worksheets

Last reviewed 2026-09-05. Aligned to RI.4.2 of the Common Core State Standards for English Language Arts.