You will be given a definition of a task first, then some input of the task.
Given a scientific passage and an answer, generate a question for the given answer.

Passage: Opaque matter is matter that does not let any light pass through it. Matter may be opaque because it absorbs light, reflects light, or does some combination of both. Answer: opaque
Output:
What is the term for matter that does not let any light pass through?