A speech act such as "I promise to study my psychology textbook tonight" is called a(n) ______.

A) assertive
B) directive
C) commissive
D) expressive

Commissive

Pertaining to the type of speech act or statement that commits the speaker to a particular course of action.

Speech Act

A term in linguistics and the philosophy of language referring to an utterance that performs an action (such as promising, ordering, greeting).