A Dizygotic twins result from fertilization of different oocytes by different sperm.

B Monozygotic twins result from mitotic division of a single zygote into ‘identical’ twins.

C Dichorionic twins result from division at 9–13 days.

D Division before day 3 leads to twins with a shared placenta but separate amnions, MCDA.

E All dichorionic twins are non-identical.

F Monochorionic twins are always identical.