Answer:
The sentence which correctly uses a pronoun in the objective case as an indirect object is the following one:
The crowd gave them a standing ovation at the end of their performance.
Explanation:
The pronoun is "them". It is an object pronoun, since it comes after a verb. In the sentence we are talking about, the main verb is "to give", and one gives someone something. If you want to know who received a standing ovation from the crowd, the answer is "them", an object pronoun, and not "they", a subject pronoun. Plus, the pronoun "them" is used as an indirect object, since it is also possible to use the construction "to give something to someone".
