Which is an example of intrasexual selection, not intersexual selection?

A) peahens choose to mate with peacocks with more showy tail feathers.
B) male elephant seals fight other males to defend a harem of females.
C) male hanging flies present nuptial gifts to females, who choose their mates on gift quality.
D) female sticklebacks mate with males who shake it the hardest.
E) male bower birds with longer tails mate with more females because they are more attractive.