Answer:
The correct answer is C. Hilda and Bryan presented his report to the entire class.
Explanation:
The pronoun his doesn't correctly agree with the antecedents Hilda and Bryan. The correct pronoun would be their and not his. Hilda is a girl, and Bryan a boy, so you cannot use the same pronoun for two different genders in this case.
The other sentences have correct agreement between their pronouns and antecedents.