Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[Q]: The sun and the moon appear to be about the same size in the sky because the moon is smaller in diameter and is closer to earth than the sun.
[A]: Which statement best explains why the Sun and the Moon appear to be about the same size in the sky?

[Q]: Producing sperm and secreting testosterone are the main functions of male reproductive system system.
[A]: Producing sperm and secreting testosterone are the main functions of what system?

[Q]: Band theory theory can explain virtually all the properties of metals.
[A]:
What theory can explain virtually all the properties of metals?