Which is NOT correct about business letter？

A.A business letter is an official correspondence between two or more parties.

B.Inquiry， recommendation or application letter all belong to the category ofbusiness letter.

C.We write a business letter when we need to buy or sell something.

D.There are certain rules you have to follow when drafting a business letter.

正确答案：We write a business letter when we need to buy or sell something.