补体活化的经典途径中，C4的激活剂是（）
A.C1q
B.C1r
C.C1s
D.C1qrs
E.C5
参考答案：C
The boss commanded that the task _____ before 5 o'clock this afternoon. [ ]
A. was finished
B. finished
C. be finished
D. should finish
ADSL具有（）KM的接入距离。
A.5~8KM
B.3~7KM
C.3~5KM
D.3~6KM
