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单选题
The signal must be given in such a precise way that the pilot cannot confuse.
A
You must give the obvious signal in a certain way in order to be seen by the pilot.
B
You must stand on a specific road, that is a clear signal for the pilot.
C
You must give the pilot the clear signal that is not misunderstood by the pilot.
答案解析
正确答案：C
