Can I go to the park, Mum?—Certainly. But you ______ be back by six o’clock.

____, a form must be filled in.

I’m sorry you’ve missed the train. It ten minutes ago.

Qingdao will spend about 80,000,000,000 yuan in building a bridge _____ the sea. [ ]

the team finished most of their research work?—Yes, but the rest rather difficult.