Answer:
B. which he bought himself, is now gone.
Explanation:
An intensive pronoun is a pronoun that adds emphasis on the antecedent. It is easy to identify an intensive pronoun by the presence of 'self/selves' in it such as "myself, yourself, themselves, himself, herself," etc.
In the given sentence formation, the intensive pronoun to complete the sentence is option B. While the rest of the options do not contain any intensive pronoun, option B has 'himself' in it. So, the full sentence will become<u><em> "Trevor's backpack, which he bought himself, is now gone."</em></u>
Thus, the correct answer is option B.
