已知f(x)dx＝56，则( )
书籍好比一架梯子，它引导我们登上知识的殿堂；书籍如同一把钥匙，__________。
I'm too tired to go any further．Let's stop and have a break．
— Yes, it made me _________ many times.
Look!There is bottle on the table．（ ）
