Professor Lee failed many times but he ________found a good way to solve the problem.
Sir, you ________ take this seat. It’s just for the old.
______ life began on earth is one of the biggest puzzles that scientist found hard ______.
Was it because his mother was ill ______ he didn’t go to school?
What ______ will it ______ whether you are a boy or a girl ? As long as you set your mind to it, nothing can be difficult.
which of the following sentences is right ?