The wire was found broken. And ______, there happened to be no one getting near.
| A．therefore | B．however |
| C．otherwise | D．fortunately |
He wondered if he could slip out of the lecture hall without anyone______.
| A．noticing | B．noticed | C．to notice | D．being noticed |
We cannot figure out ____quite a number of insects, birds, and animals are dying out.
| A．that | B．as | C．why | D．when |
We have been told that under no circumstances_______ the office telephone for personal affairs.
| A．may we use | B．we can use | C．we could use | D．did we use |