单句改错。下列句子每句均有一处错误，请指出并改正。
He came here for the purpose ofdo business.
A           B C             
错误项_______改正_________
I will give money tomedicine research.
A        B   C
错误项_______改正_________
He could be run for exercise.
A     B      C
错误项_______改正_________
Not only you but also he knowthe secret.
A        B   C
错误项_______改正______
Beijing is one of the big cities in China.
A     B    C
错误项_______改正_________