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

Ex Input:
Passage: Matter can be classified as transparent, translucent, or opaque depending on how it interacts with light. Answer: opaque

Ex Output:
Depending on how matter interacts with light, it can be classified as transparent, translucent, or what?

Ex Input:
Passage: Glutathione is a low-molecular-weight compound found in living cells that is produced naturally by the liver. Healthcare providers give glutathione intravenously to prevent side effects of chemotherapy and to prevent kidney problems. Answer: liver

Ex Output:
Glutathione is a low-molecular-weight compound found in living cells that is produced naturally by what?

Ex Input:
Passage: 23.4 Natural selection is the only mechanism that consistently causes adaptive evolution. Answer: natural selection

Ex Output:
What is the only mechanism that consistently causes adaptive evolution?