The chance of successful fertilization is approximately 18% in every cycle. Why does this statistic seem so low? All of the following statements provide a reason as to why the chance of fertilization is only 18% for every ovarian cycle EXCEPTSelect one:

a. If more than one sperm fertilize an egg, multiple embryos can result. 

b. The vagina is very acidic, killing many sperm cells.

c. Some sperm cells are not very motile, while others are formed without a tail.

d. There are two Fallopian tubes and two ovaries, but only one of them releases an ovum every cycle.