题目内容
Most airliners _____warning lights and horns.
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A voice message system on some aircraft may give a clear _____ warning indication.
To _____ the ambiguity of a horn or buzzer, a voice message system is used in most airliners.
The _____ of advanced warning systems and effective crew training has made gear-up landing accidents in large aircraft extremely rare.
In the event of failure of power system, an emergency extension system is always _____.
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