题目

I have received your letter last week.. Don’t worry about me.    31.__________I’m getting on well with my research works in the lab. But 32.___________to my surprise you say you will give up learn English.   33.___________The reason is because you have not done well in it recently       34.___________and you have lost interesting. I’m afraid I can’t agree with35.___________you. I know it is not easy to learn English, and English 36.___________is widely used in the world today and it will be important 37.___________tool in your future work.. Beside, it is becoming more and38.已知数列为等差数列，且．（1）求数列的通项公式；（2）证明 .