It was not until 1920_________ regular radio broadcast began.
| A．while | B．which |
| C．that | D．Since |
In __________ preparation for Shenzhou If, scientists need __________ knowledge of weather changes.
| A．the; the |
| B．a; / |
| C．/; a |
| D．the; a |
—Thanks so much for everything. You have certainly made my stay very pleasant.
—__________.
| A．It's my duty |
| B．It's all right |
| C．It's my pleasure |
| D．It doesn't matter |
—__________ for the fire!
—It's OK. I'll be careful enough.
| A．Look out |
| B．Watch over |
| C．Put out |
| D．Light up |
I remembered __________ the door before I left the office, but forgot to turn off the lights.
| A．locking |
| B．to lock |
| C．having locked |
| D．to have locked |
The manager __________ the workers how to improve the program since 9 am.
| A．has told |
| B．is telling |
| C．has been telling |
| D．will have told |