—There is a pen on the ground. Is it Li Long’s?—It         Li Long’s. He went to Beijing many days ago.

– Who didn’t turn off the light after school yesterday?– It ______ be Lucy. She told me she was the last one to leave the classroom.

— What does the sign over there say?— No person ______ enter the area without the official permission.

There's enough time for you to go to the airport.You        hurry now.

The police still haven’t found the lost child, but they’re doing all they             .