Topic: Interchange of Parts of Speech,

Best Answer Explained in Below-:

The correct answer is C) decisive because it is the adjective form of the noun "decision." In English, adjectives are words that describe or modify nouns, and in this case, "decisive" is used to convey the quality or characteristic of making decisions firmly and effectively.

For example, when we describe a person as having a decisive nature, we imply that they are capable of making choices quickly and confidently, often leading to clear outcomes. The other options do not serve as adjectives related to "decision."

A) "decide" is a verb, meaning to make a choice or reach a conclusion. B) "decisiveness" is a noun referring to the quality of being decisive—again, not an adjective. D) "decisively" is an adverb that describes how an action is performed—specifically, in a manner that demonstrates firm decision-making.

Thus, "decisive" is the only option that appropriately functions as an adjective to describe the nature of decision-making, making it the best answer to the question.