装备管理系统各类数据与实际误差率应低于10%，误差数据补录时限不得超过（）个工作日。
A.3
B.5
C.7
D.10
参考答案：B
Chuck Swindoll once said, “Life is 10% _____ happens to us and 90% _____we respond to it.”
A．who; why
B．what; how
C．which; when
D．that; that
煤矿井下防爆电气设备的总标志是（）。
A.Ex
B.Exl
C.Exib
