A、 To live happily.
B、 To be contented.
C、 To live and cherish what you have at the moment.
D、 To have a great ambition.

【正确答案】 C

【答案解析】细节题。原文“The happiest person is the one who enjoys what each age gives him without wasting his time in useless regrets”，可知想要成为幸福的人，应该且行且珍惜，享受当下的时光。因此，正确答案为C。

A、 A child has to go to school.
B、 A child doesn' t have enough money.
C、 A child is restricted to doing something he wants to do.
D、 A child will be punished by parents.

【正确答案】 C

【答案解析】细节题。原文“a child has his parents；he is not free to do what he wishes to do”可知小孩的自由是受限制的。be restricted to do与not free to do为同义替换。因此答案为C。

A、 Being a child is much happier than being an adult.
B、 We should enjoy what each age gives us.
C、 Being an adult should take more responsibilities.
D、 Being a child is often taken care by others.

【正确答案】 A

【答案解析】推断题。文中表明人生的每个阶段有各自的快乐和烦恼，人们应该活在当下。作者并没有认为某个阶段要比另一阶段好。所以，A项为正确答案。