Question

to migrate means to move to another place. the b and knew they wouldnt survive if they stayed put. america.
a. migrated
b. migrating
c. migration
d. migratory

Explanation:

The sentence needs a noun to follow "their annual". "Migration" is a noun meaning the act of migrating. "Migrated" is a verb - past tense, "migrating" is a present - participle form, and "migratory" is an adjective.

Answer:

C. migration