If people praise them or thank them in an especially polite way, they may become uncomfortable and not know what to say in reply.

A．Americans exchange gifts the first time they meet
B．Americans seldom give gifts except for some holidays
C．Americans often bring some gifts to their friends
D．Americans only want to get gifts from others

A．there are too many underdeveloped countries in the world
B．underdeveloped countries have low level of industrial development
C．different governments have different views about the problem
D．even developed countries may have complex problems