Answer
!.1:3
Depolarization.
As soon as the sperm touches the egg, the egg plasma membrane depolarizes. This prevents the binding of any other sperm to the plasma membrane of that egg. Then, the cortical granules in the egg cytoplasm release enzymes that cause the zona pellucida to absorb water and swell. This also helps to keep unwelcome additional sperms away from the egg.
Work Step by Step
Other factors that prevent polyspermy:
Sperms get lost in the pelvic cavity
Large numbers of sperms are killed by uterine enzymes
Many sperms get stuck in the uterine mucus
