The correct option is A collective
The correct answer is Option A - collective nouns. Words such as team, flock, fleet etc are collective nouns because they refer to a large number of people or things taken together.
Option B is incorrect because concrete nouns refer to people or things that can be experienced with the five senses.
Option C is incorrect because uncountable nouns refer to things that cannot be counted.
Option D is incorrect because proper nouns refer to people or things that are specific or unique.