再次免疫应答时产生抗体的特点是（）
A．以IgM为主
B．维持时间长
C．IgG与IgM同时发生
D．抗体效价低
E．为低性抗体
参考答案：B
- It snowed heavily last night. Is everyone m our class here today?
-Yes, and_______ of us was late for school this morning.
A．none
B．neither
C．all
D．Either
The flight will be announced soon. ____ ,please remain seated.
A．Besides
B．After all
C．Meanwhile
D．In general
