The red signal means you can shoot.

红色信号表示可以射击。

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A red signal is often used as a danger signal.

红灯常常被当作危险的信号。

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When we are driving, and we see red signal, we often are more alert.

当我们开车，看到红色的信号时，总会提高警觉。

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"I don't think we'll ever completely clear our rivers of red signal crayfish, " she said.

BBC: Study may help endangered white clawed crayfish

The native species is under threat from red signal crayfish, which were introduced to the UK in the 1970s and now dominate rivers.

BBC: Study may help endangered white clawed crayfish

The crash happened when a Thames Trains train driven by Michael Hodder, 31, went through a red signal and hit a London-bound Great Western express.

BBC: Paddington rail crash