C. Tom isn't quite happy in Denver because

1. Tom mentions his schoolmates invited him to go hiking or camping, but he was afraid they would see him as a failure.
2. He then describes his first camping experience, which involved getting lost and his backpack being conspicuous.
3. Although he eventually decided camping might not be so bad, the initial fear and his perceived failure suggest he is not entirely comfortable or happy with his new schoolmates' activities, especially if they expect him to be a proficient camper.