In Terms of Reciprocation in the United States

In terms of reciprocation in the United States:

A) gift giving is a legal and established part of the business culture and builds relationships with clients.
B) managers are known to tell people what they will give in return at the same time they ask for something.
C) it has been found that purchasing managers who receive a gift are willing to purchase services they would have otherwise declined.
D) it is assumed gift giving will lead to some form of reciprocity.