The correct option is D Collective Noun
From the given options, D is correct because collective nouns refer to a group of people or animals in a specific manner, 'crowd' refers to a particular group of people, hence it's a collective noun. Countable nouns refer to things that can be counted as individuals, example, dog/dogs. 'Crowd' cannot be counted, because it refers to a collective group, hence option A is incorrect. Proper Nouns name a specific person, place, or thing, like Asha, America. 'Crowd' does not name a specific person, but a group of people, hence it's not a proper noun and option B is incorrect. Abstract nouns refer to an idea, a state of being, a feeling, an emotion, and not a physical object. 'Crowd' does not refer to an idea, but a group of objects, the people. Hence option C is also incorrect.