ing is good exercise; ____, it doesnot pollute the air.

30．— Do the Smiths live next door to you? — No, but they____

I _______ to learn to play the piano ever since then.

It is convenient for people to work by subway. It’ssaid that The Line 4 subway in Chengdu _______by the time of 2018.

__ himself with greatstrength, he raised himself