抗体与抗原结合的部位是（）。
A.VL和VH区
B.CH1区
C.CH3区
D.CD4区
E.绞链区
参考答案：A
The student was ________ a gold cup for his excellent performance in the competition.
A．awarded
B．admitted
C．applied
D．advanced
北大校办企业上缴利税比回报学校多多少元( )
A．20亿
B．16亿
C．4亿
D．15亿
