Fertilization
Fertilization occurs when the male gamete meets the female gamete, following the sequence:
The egg is released by the ovaries and goes to the fallopian tube, where it awaits a sperm. The sperm passes through the cervix and meets the egg. This meeting of gametes is the fertilization that will form a new organism.
Therefore, the answer is "A. Sperm enters the uterus through the cervix to fuse with an egg.".