老师举手示意大家安静。

The teacher raised her hand as a ___signal for silence.

电视画面不清晰是因为信号太弱了。

The TV picture is blurry because the ___signal is too weak.

司机打转向灯示意要右转。

The driver ___signaled to turn right by using his blinker.

股市上涨是一个积极的经济信号。

The rise in stock market is a positive ___signal for the economy.