打印机的分类方法很多,从打字原理来区分,可分为( )。
A. 击打式和非击打式
B. 串行式和并行式
C. 点阵式和活字式
一个完整的磁盘存储器由三部分组成,其中____是磁盘机与主机的接口部件;____是独立于主机的一个完整的设备;____用于保存信息。
Which of the following markers is usually the first viral marker detected after hepatitis B infection?
A. HBeAg
B. HBsAg
C. HBcAg
D. Anti-HBc
E. HBeAb
Which one of the following markers is closely associated with HBV infectivity and DNA polymerase activity?
A. HBeAg
B. HBsAg
C. HBcAg
D. Anti-HBc
E. HBeAb