Identify the kind of noun. “The troupe of dancers decided to leave.”

Option B is the correct option. "Troupe" is a Collective noun. The name of a group of similar things or animals is a Collective noun. The Noun is the name of any animal, place, person, or thing. 

A collective noun refers to the collection of things taken as a whole. Examples of collective nouns include group, flock, gaggle, galaxy, etc. Usually, a collective noun is specific to the group; however, some collective nouns are common for everyone, like 'group'. For example, a group of people, a group of dogs, etc.