A bank with many teller Windows often USES electronic signs to indicate the location of the next free teller.
有许多出纳窗口的银行经常使用电子信号来指示下一个空闲出纳员的位置。
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The animal that goes to a favorite food-foraging location and sees signs that a predator was there - but not the predator itself - may be on guard the next time.
In addition, some signs in the location of the problem, such as large objects or buildings, trees and other cover, it will give people a lot of trouble.