4. They are our new members. They come from Harbin.(改为含定语从句的复合句）

They are our new members              Harbin.

3. It's a large crowd.(改为感叹句） 

               large crowd！

2. We all regard him as the best student in our class.(改为被动语态）

He                  the best student in our class.

        the tall building        ？

10. Every year,           (数百万的)tourists come to visit the Great Wall.

9. Students          (被允许)take part in making their school rules.

8. My sister _______________ (坚持)playing the piano every day.

7. John      (对……感到满意)what we're doing for him.

6. Your dress                   (与……相似）Mary's.

5. There's           (没有疑问）that he can work out the problem.