By the time I got to the airport, the plane ________.
A. took off B. has taken off C. had taken off
—Shall we stop for lunch _______ shall we drive on?
—Let’s stop for lunch, but the driver can’t drink _______ drive.
| A．and; and | B．or; and |
| C．or; or | D．and; or |
Guilin is ___ attractive city. It’s ____ nice place that many tourists go there every year.
| A．an; so a | B．a; a so | C．a; a such | D．an; such a |
_______, when Marx was already _______, he found it was important to study the situation in Russia, so he began to learn Russian.
| A．In 1870s, in his fifties |
| B．In 1870s, in fifties |
| C．In the 1870s, in fifties |
| D．In the 1870s, in his fifties |
---Where is Linda? I can’t find her anywhere. ---She ______ the flowers in the garden.
| A．waters | B．is watering |
| C．watered | D．has watered |
If we ______ take environmental problems seriously, the earth _______ worse and worse.
| A．don’t; will be | B．won’t; isn’t |
| C．won’t; is | D．don’t; won’t be |