In man, identical twins occur when
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An ovum is fertilized by a sperm and then divide into two, each forming a separate embryo
- an ovum fertilized by two sperms and then divides into two, each forming an embryo
- two ova are fertilized at the same tine each forming an embryo
- two ova are fertilized by a single sperm each forming an embryo after fertilization
- one ovum first divides into two and each half is fertilized by a sperm before developing into an embryo