Give me one good reason why I should help you.
我为什么要帮你？给我一个充分的理由。
She of all people should know the answer to that.
在所有的'人中，唯有她最应知道那个问题的答案。
Many people feel that the law should be changed.
许多人都觉得这项法律应该修改。
The treatment should be repeated every two to three hours.
这种治疗方法应该每隔两到三小时重复一次。
I think we should go back to first principles.
我认为我们应该回到基本原则上。