---I find ________ hard ________ me to understand his painting.---It’s polite ________ you to say so. His painting is nothing.
We must have the machine ____.
He didn’t enjoy the play because he ____.
The dog ____ mad(疯的).
I think _____necessary(必要的) to learn English well.
____ were all very tired, but none of ____ would stop to take a rest.