We thought we had such problems. How were we to know we were happy?
请务必花时间阅读纪念碑旁边的铭文细节。
You don't have to be a mathematician to have a feel for numbers.
想让小孩子在旅行中表现良好,可以准备一袋他们喜欢的糖果,当他/她不乖时,就向窗外扔掉一块糖。