单项选择题
A．he B．who C．which D．what
A．a great effect on everyone’s intelligence B．same effect on most persons’ intelligence C．some effect on a few persons’ intelligence D．no effect on most persons’ intelligence
A．even Americans are surprised at the big differences among themselves B．there are many differences in character in different parts of the USA C．there are many reason for the differences D．stereotypes about people are not necessarily true