Question

1. read sentence 9 from the article. comets are believed to be debris left over from the formation of planets in a solar system. to what is the underlined word referring? a small planets that began to orbit the sun with the larger ones b. asteroids from outside the solar system that became planets c. pieces of the planets that were chipped off by comets d. materials that were not incorporated into the planets

Explanation:

To solve this, we analyze the meaning of "debris" in the context. The sentence says comets are debris left over from planet formation. "Debris" here should be materials not used in forming planets. Let's check options:

• Option A: Talks about small planets orbiting, not leftover debris. Eliminate.
• Option B: Mentions asteroids from outside becoming planets, not leftover. Eliminate.
• Option C: Says pieces chipped off by comets, but debris is from planet formation, not comet - caused. Eliminate.
• Option D: Materials not incorporated into planets matches "leftover from formation". Correct.

Answer:

D. materials that were not incorporated into the planets