(d) : In human beings, ovum is released from the ovary in the secondary oocyte stage. The maturation of secondary oocyte is completed in the mother’s oviduct (Fallopian tube) usually after the sperm has entered the secondary oocyte for fertilisation. Entry of the sperm restarts the cell cycle breaking down $MPF$ (M­phase promoting factor) and turning on $APC$ (Anaphase promoting complex). Completion of meiosis $II$ converts the secondary oocyte into a fertilised ovum (egg) or zygote (and also a second polar body).