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

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

[Q]: Passage: All compounds form when atoms of different elements share or transfer electrons. In water, the atoms share electrons. In some other compounds, called ionic compounds , atoms transfer electrons. The electrons actually move from one atom to another. When atoms transfer electrons in this way, they become charged particles called ions. The ions are held together by ionic bonds. Answer: ions
[A]: When electrons move from one atom to another, they become what?

[Q]: Passage: In normal faults , the hanging wall drops down relative to the footwall. Normal faults are caused by tension that pulls the crust apart. This causes the hanging wall to slide down. Normal faults can build huge mountain ranges in regions experiencing tension ( Figure below ). Answer: ground tissue
[A]:
What makes up most of the inside of a plant?