All of the Following Statements About Twins Are Correct Except

Multiple Choice

All of the following statements about twins are correct except

A) when a single fertilized ovum divides into two separate cells, it results in monozygotic twins
B) when two different eggs are released and fertilized by two different sperm, the result is dizygotic twins
C) in some twin pregnancies, one of the twins "vanishes" when each of the twins possesses a different variant of a gene on the same chromosome
D) monozygotic twins can be the same sex (two boys or two girls) or different sexes (one boy and one girl)