Given a scientific passage and an answer, generate a question for the given answer.

Passage: the fact that stars are made up of very lightweight hydrogen gas. Answer: hydrogen
What type of gas are stars made up of?

Passage: Runoff is likely to cause more erosion if the land is bare. Plants help hold the soil in place. The runoff water in Figure below is brown because it eroded soil from a bare, sloping field. Can you find evidence of erosion by runoff where you live? What should you look for?. Answer: erosion
Runoff is likely to cause more what if the land is bare?

Passage: Humans have been studying the night sky for thousands of years. Knowing the motions of stars helped people keep track of seasons. With this information they could know when to plant crops. Stars were so important that the patterns they made in the sky were named. These patterns are called constellations . Even now, constellations help astronomers know where they are looking in the night sky. Answer: constellations
What are observable patterns of stars found in the night sky called?