The infinitive is the most versatile verb form because it can be used as

Question

A. a verb, an adjective, or a preposition
B. a verb, a noun, an adverb, or an interjection
C. a verb, an adverb, or a conjunction
D. a verb, a noun, an adjective, or an adverb

Answer 1

http://www.chompchomp.com/terms/infinitive.htm

Answer 2

is the answer D