Not all the patents________ have been recognized.
| A．to be examined | B．being examined |
| C．examined | D．having been examined |
_______ the news, they are very happy.
| A．Hearing | B．Heard | C．Hear | D． To hear |
We last night, but we went to the party instead.
| A．must have studied | B．might study | C．should have studied | D．would study |
The reason_______ he didn’t come was that he was injured.
| A．that | B．why | C．because | D．when |
There is no doubt _________ the world climate has been changing in recent years.
| A．that | B．what | C．if | D．whether |
Will you help him________ you see an old man in trouble ?
| A．though | B．so | C．because | D．when |