In female reproduction, after ovulation, the oocyte remains viable for fertilization for about 12–24 hours. What is the physiological basis for this limited survival?

Correct option is B

The oocyte has limited cytoplasmic energy reserves and metabolic activity declines rapidly after ovulation, making it viable only for 12–24 hours.
Explanation of options: (a) ✘ Zona pellucida persists longer and is not the main limiting factor. (b) ✔ Correct; reduced metabolic activity and mitochondrial energy cause oocyte death in 12–24 hr. (c) ✘ Acrosomal receptors are on sperm, not on oocyte. (d) ✘ Progesterone acts on endometrium, not directly on oocyte survival.