大多数人注射乙肝疫苗（抗原）后，引起体内产生[ ]
A．相应抗体
B．生长激素
C．记忆B细胞
D．乙肝病毒
AC
Don't be angry with us. We ________ with you together, but we were busy with our final reports when you called in.
A．would eat out
B．must have eaten out
C．should eat out
D．could have eaten out
简述链传动的张紧方法。
