Answer:
D, When food sources are scarce.
Step-by-step explanation:
(This part is optional)
Cannibalism usually happens when food sources are scarce. This is because if for example, a lion was hunting for food but (for whatever reason) they ran out of meat. Then, they would probably, like animal nature, want to keep surviving. And if food sources are running out or gone, their only hope is to eat their own kind.
Hope it helped!