I don 't know the man． The man is talking with our headteacher（改为含有定语从句的复合句）
I don't know the man talking with our headteacher．
If we work hard together， our actions can make a d to the world and lead to a better future．
Do you know w baseball this is？ Does it belong to Jim？
The Russian soup s very nice， I can't wait to drink it．
Jack comes from America， but he knows many （传统）folk stories about Chinese festivals．
Could you get me an （介绍） to your friend？