可用于预防甲型肝炎的被动免疫制剂是( )
A．甲型肝炎减毒活疫苗B．乙型肝炎基因重组疫苗C．血清白蛋白D．丙种球蛋白E．核酸
参考答案：D
Our club is open to adults only. ______ your children have entered without permission. [ ]
A. There seems that
B. It seems to be
C. There seems to be
D. It seems that
SSB发射机通常采用三搬频的高中频方案，其中间频率是指（）
A、第一调制器的输入频率
B、第二调制器的输入频率
C、第三调制器的输入频率
D、第三调制器的输出频率
