Final answer:
The word that is a collective noun in the given options is 'a) crop'. A collective noun is a singular noun that represents a group of individuals or things.
Step-by-step explanation:
The word that is a collective noun in the given options is 'a) crop'.
A collective noun is a singular noun that represents a group of individuals or things. In this case, 'crop' refers to a collection of plants or agricultural produce. For example, we can say 'The farmers harvested a bountiful crop this year.'