单项选择(每题1分)He often speaks of the trouble he _______ to help the orphan.
— Are you going to take part in the speech contest? — ___________. It’s too good an opportunity to miss.
— How about camping this weekend, just for a change? — OK, ______ you want.
—Was it under the tree ______ you went away talking to a friend? —Sure. But when I got back there, the bike was gone.
Whitney Houston’s sudden death suggests that drug abuse is such a serious problem ______ we should deal with properly.
The argument is extremely heated ______ there are necessary conditions of existence such as water on the Mars.