I saw Li Ming________near the river on my way home．
| A．plays |
| B．playing |
| C．to play |
| D．played |
Take a map with you while traveling ________ you have a guide or know the city well．
| A．since | B．if | C．unless | D．because |
- The air pollution is terrible.
- It will be worse ________ we take action to protect the environment.
| A．if | B．unless | C．until | D．when |
She has worked in this factory ______ she came here in 2010.
| A． when | B． since | C．for | D．from |
-I’m afraid the meeting has begun. -Don’t worry. It ___ until the bell ____.
| A．doesn’t begin ;rings | B．won’t begin ; will ring |
| C．won’t begin ;rings | D．doesn’t begin ;will ring |
In summer milk will quickly go bad _____it is put into a fridge.
| A．though | B．unless | C．because | D．once |