I had the same question, it's most likely B.
Answer:
How do you explain dark matter?
Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. Dark matter is material that cannot be seen directly. We know that dark matter exists because of the effect it has on objects that we can observe directly.
They do not move they stay in the same same place it may look like they move because of the earth rotation