Multiple choice Lake Baikal, in Russia, has more species of worms than other similarly deep and cold lakes because

a. Migratory birds introduced worms to this lake.

b. A large mammal died at its edge and worms found a plentiful food source.

c. This lake did not experience a glaciation period.

d. Worm species migrated from nearby lakes.

e. Worm species were introduced to the lake by local human populations.