题目内容：

根据句意和语法, 在空白处填入适当的内容或括号内单词的正确形式(不多于3个单词)。

1.I was most___________(grate) to John for his kindness of sending me the book immediately.

2.The Great Wall is ___________a well－known tourist attraction that millions of people pour in every year.

3.After a long period of hard work, the boy is _____________________ (gradual) catching up with the others in his class.

4.I like getting up very early in summer. The morning air is good  _______________(breath).

5.As you know, he left three years ago. He __________________ (not write) to me ever since.

6.We are flying at ______ altitude of 20, 000 feet. I feel very nervous.

7.The weather is even colder with the wind________________(blow) .

8.—Tom, you are late again.

—Yes, that's _______________ my car broke down on the way.

9.My first _____________ (impress) of him was that he was a kind and thoughtful young man.

10.I explained that problem to the students again ___________ their request.