The problem of the present world is that those who are imaginative have little experience_________those who are experienced have weak imagination.
| A．unless | B．although | C．because | D．while |
Carbon dioxide(CO2)_______ from burning fuels is the most common of the so-called greenhouse gases.
| A．producing | B．having been produced |
| C．to be produced | D．produced |
We must apply what we have learned to our daily work because in no case_____ from practice.
| A．should theory separate | B．theory should be separated |
| C．theory should separate | D．should theory be separated |
Mrs. White found her husband surrounded by letters and papers and_______ very worried.
| A．look | B．looked | C．looking | D．to look |
----What are you busy with?
---- The conference_______ in our city next week.
| A．held | B．to be held | C．be holding | D．will be held |
_______ of danger in the street at night, she had to go home with a friend_______ her.
| A．Warned; accompanied | B．Having warned; accompanying |
| C．Warning; accompanying | D．Having been warned; accompanying |