The correct option is B its
Option B is the correct answer. When a pronoun represents a Collective Noun, it should be in singular number and neuter gender, if the collective noun is viewed as a whole. A pronoun is a word or phrase used in place of a noun. Collective nouns are words used for individual things that include more than one person, animal, thing, place, or idea. In this sentence, the 'class' is viewed as a whole collective noun, so, the pronoun representing it should be a neuter singular pronoun. Thereby, 'its' is the correct answer. 'Their' is plural in number, so Option A is incorrect. Option C, 'his' is of masculine gender, hence, its incorrect. Therefore, the sentence should read: The class was punished for its misbehavior.