. _______ different kinds of pianos, the workers farther improved their quality.
. —Have you finished your composition? —Yes, I _____it in twenty minutes.
It’s important that he_____ English well.
I’m sorry that I can’t help _____ trees because I am busy with the homework.
—What led to his success ? —He succeed _____ working hard .
.I don’t think that the sentence need ______again.