Answer:
The dependent clause is: "when you think about him" (option 1).
Step-by-step explanation:
A dependent clause is a group of words that contains a subject and a verb but cannot stand alone as a sentence. It depends on an independent clause to form a complete thought. In this case, "when you think about him" is a dependent clause because it does not make complete sense on its own and is dependent on the rest of the sentence for context.