随着夜幕降临，城市灯光开始闪烁。

As ___darkness ___fell, the city lights started to twinkle.

夜幕降临时，我们决定扎营过夜。

As ___darkness ___fell, we decided to set up camp for the night.

当夜晚降临时，沙漠中的温度显著下降。

When ___night ___falls, the temperature drops significantly in the desert.