设函数，在x=0处连续，则a等于( ) A．0 B． C． D．2

—Is that your teacher?

—That_____be Mr.Wang. He has gone to Japan with his wife.[ ]

A. can't

B. mustn't

C. may not

How long have you _______?

A．married

B．be married

C．got married

D．been married

下面的哪一项不是淋巴结的功能（）

A.过滤淋巴液，清除异物

B.进行免疫应答

C.产生抗体

D.淋巴结可以产生淋巴细胞，但不能储存淋巴细胞

E.形成红细胞、粒细胞及血小板

转主寄生

Ethernet的MAC地址长为______位。