One possible version:

Dear Jack,

I was so pleased to hear from you and am writing to tell you something about my school and school life.

Our school is a famous school with a history of 100 years . There are 48 classes with 3000 students and 220 teachers in it. The school is tidy and beautiful .Teachers here are careful in teaching and patient to every student.. The main subjects we study in senior high school include Chinese, math, English , physics, chemistry and computer. I like math and computer best and I am very good at them. But I have difficulty in English study . I hope you can give me some advice on how to learn English well. In my spare time, I enjoy listening to popular music and playing basket ball with my classmates .

I hope you come to China some day.

　　　　　　　　　　　　　　 　　　　　　　　　　Yours sincerely,

Li Hua

90. He was generous with his time , to (for )which I was grateful.　

89.We saw many yaks and sheep eat (eating )green grass.

88. Along the way, children dressed∧(in) long wool coats stopped to look at us .

87. My sister doesn’t; care for (about ) details .

86. Ever since middle school , my sister and I ∧(have)dreamed about taking a great bike trip.

85. The USA is a large country which(把which 换成where 或在which 前加in ) many different dialects are spoken.

84.On TV and the radio, you will hear differences in the way which (删除which 或在which 前加in 或将which 改为that )people speak.

83. Believe it or not , there is no such a thing as standard English .