Select the appropriate word to fill in the blank: _____ choice was to go to the movie.

The correct choice to fill in the blank is "C." This is because the sentence appears to refer to a collective decision made by a group of people, which is indicated by the use of the pronoun "their." This pronoun conveys that the choice belongs to multiple individuals, characteristic of a plural possessive.

Using "his" or "her" would limit the choice to a single individual, which does not align with the implication of a group decision in this context. "Its" is typically used to refer to non-human entities or singular things, which also would not fit a scenario regarding a personal decision about going to a movie. Thus, "their" effectively captures the communal aspect implied in the sentence.