Male northern elephant seals (Mirounga angustirostris) compete with one another for territories along the beach. Males defend these territories throughout the breeding season. The males that win the male–male competitions defend the "best" territories, and have access to females that stay in that territory of the beach. The females land on the beach during mating season, choosing which territory of the beach to join. They then disproportionately breed with the male that defends that area of the beach. At what point may intersexual selection occur in these elephant seals?
A. when the female is swimming to the beach

B. when the female leaves the beach after mating with a male

C. when the male defends his group of females against a different male

D. when the female lands on the beach and chooses her resting location

E. when the male mates with a female within his group

In elephant seals, the male arrive the beach first and start establishing its territory. Once their territory is established female elephant seals starts arriving at the beach and prefer mating with the male who can defend their territory or females in his territory from other males. All females in the territory of specific male mate with the male give birth to their pups and after staying for few months move back into the water.

hence, option C is correct