傍晚时分，天空渐渐变暗了。

The sky was ___darkening as evening approached.

持续的冲突正在使该地区的和平前景变得黯淡。

The ongoing conflict is ___darkening the prospects for peace in the region.

随着雾越来越浓，远处的建筑物开始变暗。

As the fog thickened, the buildings in the distance began ___darkening.