It took him one hour________his homework．
| A．do | B．to do | C．doing | D．to doing |
These boxes ______ for keeping the food clean and cool.
| A．use | B．are used | C．have used | D．were using |
My parents asked me ______ my sister with her schoolwork.
| A．help | B．to help | C．helping | D．helped |
Sir, would you mind not _____ here, please?
| A．to smoke | B．smoke | C．smoking | D．smoked |
Miss Green isn’t in the office. She_______ to the library.
| A．went | B．was | C．has gone | D．has been |
I didn’t hear your call because I ______ to music at that time.
| A．listen | B．will listen | C．am listening | D．was listening |