A.A.they reply very quickly in a hurry
A.A.need more time to get used to American simple greeting
C.C.Americans in high ranks must use formal words in greeting.
A.A.they don’t know what to say in reply
B.B.Americans seldom give gifts except for some holidays.
I'm American & I came to china to learn some chinese,but it's kinda wrong because we usually give gifts on X-mas.