The water supply has been cut off temporarily because the workers________one of the main pipes (2013·天津，13)

He should________his attention________the main problems. [ ]

There ________ be any difficulty about passing the road test since you have practised a lot in the driving school.

___ their final medical check,the astronauts boarded their spacecraft

Let’s learn to use the problem we are facing _____ a stepping-stone to future success[ ]