______ it ______ for your help, I couldn’t have made any progress.
_________ many times, but he still couldn’t understand it.
It is to read the books our teacher recommended , for they are well _____ reading.
He was so __________ a key university that he would work until late into the night.
-Look! Everything here is under construction. -Oh, has the building once _________ for exhibition been pulled down, too?
_________ the floor, I found his pen lying on the ground.