作为机体获得对HBV免疫力及乙型肝炎患者痊愈的指标是( )
A.HBsAg(+)B.抗-HBs(+)C.抗-HBc(+)D.HBeAg(+)E.抗-HBe(+)
参考答案:B
— What are you doing? — I'm _________ nine postcards to my mother.[ ]
A. write
B. writing
C. to write
下图是课本中的几个实验,演示磁场对通电导体有力作用的是
A. B. C. D.