To answer this question, we need to understand possessive pronouns.
The correct answer is C) his.
Explanation for each option:
A) him - "Him" is an objective pronoun and is used when the person is the object of the sentence. It is not appropriate in this context.
B) their - "Their" is a possessive pronoun used to indicate possession by multiple people. It is not appropriate in this context.
C) his - "His" is a possessive pronoun used to indicate possession by a male singular noun. In this case, "his" correctly shows that the car is old.
D) it - "It" is a pronoun used to refer to a non-living thing or an animal. In this context, "it" correctly refers to the car.
Therefore, the correct answer is C) his, as it correctly indicates that the car is old.