入侵检测系统(IDS)是防火墙的合理补充,是防火墙之后的第二道安全闸门。
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The boy acted ____ he had never lived in Canada before.
A. as though
B. even if
C. as
D. since
____ to the doctor right away, he might have been alive.
A. If he went
B. Were he gone
C. Should he have gone
D. Had he gone
The secretary suggested that they ____ the men in at once.
A. had brought
B. should have brought
C. brought
D. bring
If we ____ here ten minutes earlier, we ___ the bus.
A. arrived/would catch
B. arrived/would have caught
C. had arrived/had caught
D. had arrived/would have caught
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