The place ________ the bridge is supposed to be built should be _________ the cross-river traffic is the heaviest.
(2013·全国Ⅱ,6)Since nobody gave him any help, he ________ have done the research on his own.
—You needn't take an umbrella.It isn't going to rain.—Well, I don't know.It ________ do.
When I was a child, I ________ watch TV whenever I wanted to.
I should not have laughed if I ________ you were serious.
The door ________ open, no matter how hard she pushed.