【正确答案】 B

【答案解析】[听力原文]26-28
Comparatively speaking, Americans give gifts on a relatively small number of occasion and to a relatively small circle for people. Offering gifts to people who do not expect them can cause mutual embarrassment and can even lead to the suspicion that the gift-giver is seeking to influence the recipient in an inappropriate way.
Generally, Americans give gifts to relatives and close friends. Frequently they give gifts such as flowers, wine or candy to hostesses. They do not normally give gifts to teachers, business colleagues, or other people who might be in a position to grant or withhold favorable treatment. In fact giving gifts to people who are in a position to grant or withhold favors can be regarded as an improper effort to gain favor.
Christmas comes close to being a national gift-giving day in America. Except for those non Christians, Americans exchange gifts with relatives, schoolmates, and close friends. Other gift-giving occasions are days that are special to the recipient: birthdays, graduations, weddings, and childbirths. A "house-warming" gift is sometimes given to people who have moved into a new house.
Americans try to select a gift they believe the recipient could use or would enjoy. People are not expected to give expensive gifts unless they can readily afford them.
Americans commonly send a Christmas card to each of their acquaintances and sometimes to business colleagues as well.
26. Why don't Americans often give gifts to their teachers?