The correct answer is B. The long list of activities the child gives.
Explanation
The main idea of the cartoon is the quantity of activities that the boy did in his vacations and his expectation to start school again. Also, it can be infered that the boy was so busy during vacations that the schools is like a rest for him. To explain this idea, the author used the long list of activities that the child did during his vacations. So, the correct answer is B.