The best answer to me looks like C.
Only 200 out of 2 000, 000 sperm cells reach the ovum. And only one (in exception to very rare cases of two) sperm cells actually participate in the process of fertilization. In comparison, an average female only produces 400 of egg cells during their lifetime, but the eggs cells are significantly larger than sperm cells.
I think genetic variation, but i'm not completely sure
Answer:
A scope built of two systems of lenses ... ==> Compound light microscope
Explanation:
