How soon after ovulation can an egg be fertilized? Where does fertilization occur, and how do twins come about? a) 12-24 hours; uterus; fertilization of two eggs b) 24-48 hours; fallopian tube; fertilization of two eggs c) 12-24 hours; fallopian tube; fertilization of one egg splitting into two d) 24-48 hours; uterus; fertilization of one egg splitting into two