He left home without saying a word, and _______ worries many people and is to be found out.
| A．where he has gone | B．where did he go |
| C．which place has he gone | D．where has he gone |
He looked around and caught a man ______ his hand into the pocket of a passenger.
| A．put | B．to be putting |
| C．to put | D．putting |
______ their service, the workers of the hotel are active in learning English.
| A．Improving | B．To improve |
| C．Improve | D．Having improved |
_____ the flies out, we had to shut all the doors and windows.
| A．Keep | B．To keep |
| C．Keeping | D．Having kept |
_____ late in the morning, Mr. Smith turned off the alarm.
| A．Sleep | B．To sleep |
| C．Sleeping | D．Having slept |
______ French well, she went to France to live with his cousins.
| A．Study | B．To study |
| C．Studying | D．Having studied |