Blue Whales, the World's Largest Animal, Occur in All Oceans

Blue whales, the world's largest animal, occur in all oceans except the Arctic.Before whaling, there were more than 250,000 blue whales.By 1967, when the species received worldwide protection, they were nearly all gone.Blue whale populations are recovering slowly compared with other whale species, such as humpbacks.This is most likely because

A) they are subjected to ocean challenges not felt by other whale species.
B) they reproduce more slowly than smaller species.
C) they are slower and easier for whalers to catch than smaller species.
D) restrictions on whaling have limited their ability to migrate.
E) whalers are now preying on the blue whales' food source.