______ I am willing to help, I do not have much time available.
| A．Unless | B．If |
| C．While | D．Since |
As your spoken English gets better, so ___ your written English.
| A．will | B．do | C．is | D．has |
I have only one day left ___ traveling to Kunming and then flying back home.
| A．when | B．as | C．before | D．while |
This is our contribution to ________ world of the 21st century, ________ world of independence and mutual understanding.
| A．the; / | B．/; a | C．a; the | D．the; a |
—She was late for the party.
—That’s _________she had forgotten the exact time.
| A．why | B．how | C．because | D．whether |
It_________ to me that I should pay a visit to my friend Jane.
| A．happened | B．supposed | C．proved | D．occurred |