Correct Answer - Option 3 : Sailor: crew
The logic followed is:-
A group of fish is called shoal.
Similarly, a group of sailors is called crew.
Hence, the correct answer is Sailor : crew
Herd : It represents a group of animals of same species, especially those that live together or are kept together as livestock.
Example: A herd of elephants, a herd of sheep, etc.
So, it is not particular to any animal.
A herd or group of sheep is called flock.