The Major Reason for the High Failure Rate for Coitus

Multiple Choice

The major reason for the high failure rate for coitus interruptus is that

A) only very sexually experienced men know when they are about to ejaculate.
B) sperm may be present in pre-ejaculatory secretions.
C) vaginal contractions may squeeze out semen before ejaculation.
D) vaginismus may prevent the penis from being withdrawn.