The type of verb that typically includes the word "to" is C. infinitive.
The infinitive is the base form of the verb. Moreover, the present infinitive can have the form of "to-infinitive" or the form of the "zero infinitive" (without "to"). The first form is frequently used and, for that reason, the infinitive typically includes "to". Furthermore, the "to-infinitive" can function as subject of the sentence, direct object and even as object complement. Some of the verbs that can be followed by a "to-infinitive" are refuse, propose, want and decide.
