Q.Polyspermy (entry of more than one sperm into the ovum) is chiefly prevented by

[!TLDR]

The cortical reaction alters the zona pellucida immediately after the first sperm fuses with the oocyte, preventing any further sperm from enterin …

As soon as the first sperm's plasma membrane fuses with the oocyte's plasma membrane, cortical granules just beneath the oocyte surface release their contents into the space around the oocyte. This cortical reaction chemically modifies and hardens the zona pellucida so that it can no longer be penetrated by any other sperm still attached to it, which is the principal block to polyspermy. It is not brought about by uterine contraction, by the first sperm's own acro …

Identify the specific event (cortical granule release -> zona pellucida hardening) that follows immediately after the first successful sperm-oocyte membr …

Confusing the acrosomal reaction (a sperm digesting through the corona radiata/zona pellucida to reach the oocyte) with the cortical reaction (the oocyte's own response, after fusion, that bloc …