__________ the students who have taken part in the sports game is unknown.
A. A great number of B. A great deal of
C. A large number of D. The number of
_______, the more exercise you do, the richer your knowledge will be.
A. It is known to all B. Which is known to all
C. As we all know D. As is known to all that
His mother happened _______ when his program was shown on Channel Young.
A. watching TV B. to watch TV
C. to be watching TV D. being watching TV
By the time he was ten, Edison _________ experiments in chemistry.
A. had already done B. already had done
C. was already doing D. already did
The businessperson wanted to sell his goods fast; ______, he chose his partner with great care.
A. therefore B. otherwise
C. for D. however
假定你是李华，希望通过外籍教师Peter找一位英语笔友。请写一封短信，描述一下你理想中笔友的条件，并说明为什么选这样的笔友。具体条件包括：
年龄；
性别；
爱好
注意：1. 字数100左右；
2. 可以适当增加细节，以使行文连贯；
3. 开头和结尾已写好。
Dear Peter,
I am writing to ask whether you are able to do me a favor.
Best regards,
Li Hua
