plunge

温度突然急剧下降，让我们措手不及。

The temperature took a ___plunge, catching us by surprise.

股市突然暴跌让许多投资者措手不及。

The sudden ___plunge in the stock market caught many investors off guard.

温度骤降，水银柱迅速跌落。

The temperature suddenly dropped, causing the mercury to ___plunge rapidly.