The eggs of the cuckoo (koel) have evolved to resemble crow's eggs in size and color. If the parasite bird has laid its eggs in the nest of host and lets the host to incubate them. This is an example of:

Brood parasitism

The correct answer is Option (4) → Brood parasitism 

Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them. During the course of evolution, the eggs of the parasitic bird have evolved to resemble the host’s egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest. Example:  The movements of the cuckoo (koel) and the crow during the breeding season (spring to summer) and watch brood parasitism in action.