防劫持指标：针对重要通信保障对象的路由劫持事件从响应开始至处理完毕平均耗时<（）分钟。
A.10
B.20
C.30
D.40
参考答案：B
A heavy learning burden leads to unhealthy behaviors such as poor eating habits, which ___ damage the health of students.
A．in its turn
B．in return
C．in turn
D．by turns
相同浓度和剂量的局麻药，毒性最小的是（）。
A.利多卡因
B.普鲁卡因
C.地卡因
D.布比卡因
E.丙胺卡因
