以下哪些是主动免疫制剂（）。
A.乙肝疫苗
B.转移因子
C.白喉类毒素
D.白破联合疫苗
E.白喉抗毒素
参考答案：A, C, D
Every few years, the coal workers their lungs X-rayed to ensure their health.
A．are having
B．have
C．have had
D．had had
以下哪个是指事字（）
A.信
B.皿
C.亦
D.疽
