You never know how much difficulty we had the problem. Luckily, we managed to solve it with Mrs Wu’s help.
He didn’t go to bed _______ his mother came back.
It is ___________ to hold the water.
You must have breakfast, _________ you may have a stomachache.
It is difficult ________me _______ English well. But I’ll study harder.
Don’t swim here ,or you may be __________.