1. Early next morning, she heard planes passing overhead and wondered how she could send a signal.
    第二天清晨，她听到头上有飞机飞过，却不知道怎样才能发出信号，

2. Early next morning, she heard planes passing overhead and wondered how she could send a signal.
    第二天一大早，她听到头顶上有飞机飞过，但不知道怎样才能发个信号。

3. But we are the ones who signal to businesses that what they are doing is okay — every time we buy their products.
    每当我们购买他们的产品时，我们就在向企业发出信号，告诉他们可以这样做。

4. Was it the signal?
    这是那信号吗?

5. The soldiers lay in ambush, waiting for the signal to open fire.
    士兵布下伏兵，等待开火的信号。

6. Don't be alarmed by the bells ringing in Singaporean taxis, which are simply a signal warning drivers they have exceeded the speed limit.
    坐在新加坡的出租车里，不要被铃声吓着，那只是个信号，警告司机车已经超过限制速度了。

7. Fortunately, a pilot saw the signal and sent a message by radio to the nearest town.
    幸运得很，一位飞行员看到这个信号，用无线电给最近的城镇发了报。