Final answer:
Trevor lost touch with his dad after his parents' divorce.
Step-by-step explanation:
The answer to the question is c) After his parents' divorce. In the given options, this is the only scenario that directly implies loss of touch with Trevor's dad. When parents get divorced, it is common for the child to lose regular contact with one parent or have limited communication. The other options, a) After his dad's death, b) When he moved to the United States, and d) Trevor never lost touch with his dad, do not explicitly indicate separation or loss of touch.