Which of the following describes the underlined phrase?

This is the week Jim plans "to work."

a. participial

b. adverbial

c. infinitive

d. prepositional

Of the following what describes the underlined phrase "to work" is infinitive.

When the verb commences with 'to' it is known as an infinitive verb. In an infinitive phrase, it includes the infinitive with the addition to complements or modifiers. An infinitive phrase can function as an adjective, adverb, and noun. An infinitive phrase that functions as a noun can act as a predicate nominative, subject or direct object.