Dizygotic Twins Develop from Two Eggs Fertilized by Two Separate

Multiple Choice

Dizygotic twins develop from two eggs fertilized by two separate sperm; they have, on average, 50% of their genes in common. Monozygotic twins develop from a single egg, fertilized by a single sperm, that splits into two embryos; they have 100% percent of their genes in common.
-Why are monozygotic twins genetically identical, whereas dizygotic twins have only 1/2 of their genes in common on average?

A) Monozygotic twins tend to look more similar.
B) Monozygotic twins are always the same sex.
C) Dizygotic twins arise more frequently with older mothers.
D) Monozygotic twins develop from a single embryo, whereas dizygotic twins develop from two embryos.