单项选择题
A．the part that birth plays B．the importance of their positions C．the role of environment on intelligence D．the importance of their intelligence
A．give up their college education B．learn from other students C．feel happy because they are in college D．try hard before giving up
A．there is less trading business B．there used to be more social activities in the old days C．supermarket managers has more problems D．there is less personal contact between manager and customer