---Will you please show me how to operate the new machine? ---Sure. It’s a piece of cake. Now let me tell you _____ to do first.
It is difficult __________ you ___________ finish the work in a week.
I can’t understand ____________ the boy alone.
They asked many questions ___________ had nothing to do with that topic.
_____________ is necessary __________ he trains himself before the Guangzhou Marathon.
___________ a sportsman is a hard job, but you are very excited if you are successful in ____________a good medal.