Correct Option: D

A twin is one of two offspring produced in the same pregnancy and developed from one oocyte (monozygotic) or from two oocytes (dizygotic) fertilized at the same time. Dizygotic twins or fraternal twins are heterologous twins developed from two separate oocytes fertilized at the same time. They may be of the same or opposite sex, differ both physically and genetically, and have two separate and distinct placentas and membranes, both amnion and chorion. These twins can accept grafts from each other as they have identical MHC haplotypes and identical T_H cells.