Detailed Instructions: Given a scientific passage and an answer, generate a question for the given answer.
Q: Passage: Most scientists who study dark matter think it is a combination. Ordinary matter is part of it. That is mixed with some kind of matter that we haven't discovered yet. Most scientists think that ordinary matter is less than half of the total matter in the Universe. Answer: less than half
A:
Most scientists think that ordinary matter makes up how much of the total matter in the universe?