Sexual selection results in nonrandom mating. Indicate which type of sexual selection is being exhibited in these examples.
Intersexual:
Intrasexual:
Both:

a. Nest building of male Gilded Flicker
b. Mating of Male Bullfrog
c. Long Tail of male peacock.
d. Large claws in male lobsters
e. Sparring ability of male kangaroos.
f. Strength and antler size of male elk