Fish hatchery workers know that if they want artificially spawned salmon to return to a specific stream to spawn when they reach adulthood, the workers have to raise the fry (baby salmon) in water from that stream during a certain critical time in their early development. this is a clear demonstration of
a. trial-and-error learning
b. operant conditioning
c. imprinting
d. habituation

c. imprinting  

Explanation:

Imprinting is the object of study of ethology, which is related to animal behavior. In the early stage of an animal's life, imprinting is an essential and most conducive phase for learning and subsequent development. The two main types of imprinting are sexual and filial.  In sexual imprinting, a young animal learns the traits it seeks in a mate. Affiliate imprinting is the learning of a offspring from his / her parent.

In the case of the salmon fish situation, the need for workers to raise fingerlings (salmon) in stream water during a certain critical period in their early development is an example of imprinting. In this case, imprinting is necessary for the development of this animal in a different environment from the one it was raised.

meiosis is the first to occur after the nuclei of opposite of opposite mating types fuse