Step-by-step explanation:
In English, "to improve" is an infinitive in grammar. Therefore, the correct answer is (C) Infinitive. Infinitives are the base form of a verb preceded by the word "to," and they can be used as nouns, adjectives, or adverbs. In the case of "to improve," it functions as the base form of the verb "improve" and can be used to express purpose, intention, or as the base form before additional verb forms or complements.