An infinitive can be used as all of the following except as a noun, as a direct object, as an adverb

An infinitive can be used as all of the following except as a direct object. An infinitive can be used as nouns, adjectives, or adverbs. Option B is correct.

An infinitive will almost always begin with "to" followed by the simple form of the verb.

Whe it works as an adverb, it adds information about the verb. When it works as an adjective, it modifies a noun of a sentence.

Because an infinitive is not a verb, you cannot add s, es, ed, or ing to the end

yes, it can be both.

#1  sara was always tasked with selecting birthday presents for her friends and family because everyone admired her  impeccable taste. 

impeccable (adj): perfect, flawless

#2  they moved to the united states many years ago, but their  insular  attitudes made it difficult for them to socialize. 

insular (adj): isolated; separate

#3  the professor explained the  semantic  relationship between the two nouns used in the sentence. 

semantic (adj): related to words or the meanings of words 

happy to : )