Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The question asks for the noun form of the verb "prosper." Among the options provided, "prosperity" is the most appropriate choice.

"Prosper" is a verb that means to thrive or succeed, especially in financial or material terms. The noun form of a word generally denotes a person, place, thing, or idea related to the action of the verb. In this case, "prosperity" encapsulates the state or condition of having success or wealth, making it a direct derivative of the verb.

The other options, while related, do not serve as the noun form of "prosper." "Prosperous" (B) is an adjective describing something characterized by success or wealth, while "prosperously" (C) is an adverb that describes the manner in which an action is performed, typically in a way that yields prosperity. "Prosperousness" (D) indeed captures a state associated with being prosperous, but it is less commonly used compared to "prosperity." Therefore, "prosperity" (A) is the most fitting and widely recognized noun form of "prosper."