Final answer:
The best phrase illustrating the theme of homesickness is the dialogue expressing the student's conflicted feelings about missing family yet wanting to remain at camp to prove resilience.
Step-by-step explanation:
The phrase that best supports the feeling of homesickness referenced in Part A is: "Please don't call my parents," he whispered hoarsely. "I miss my family, but I don't want to go home. I begged them to let me come to camp, but my mom just said I'd get so homesick I'd be back in two days. This is my first time away from home." This passage encapsulates the emotion of missing one's family combined with the desire to stay and prove oneself capable of being away from home, which is a nuanced aspect of homesickness.