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

Ex Input:
Passage: Density is defined as the mass of an object divided by its volume. Propose a unit of density in terms of the fundamental SI units. Answer: volume

Ex Output:
Density is defined as the mass of an object divided by its what?

Ex Input:
Passage: Mouth Brooding. Some species of fish carry their fertilized eggs in their mouth until they hatch. This is called mouth brooding. If you look closely, you can see the eggs inside the mouth of the cardinalfish pictured here. Answer: mouth brooding

Ex Output:
Some species of fish carry their fertilized eggs in their mouth until they hatch; this is called what?

Ex Input:
Passage: The structure of a mitochondrion is defined by an inner and outer membrane. This structure plays an important role in aerobic respiration. Answer: aerobic respiration

Ex Output:
The structure of mitochondrion plays an important role in what?