雨滴轻轻敲打着屋顶。

The raindrops ___thrummed softly on the roof.

她心不在焉地拨弄着尤克里里的琴弦。

She was ___thrumming the ukulele strings while lost in thought.

引擎的低沉嗡嗡声在安静的车间里回荡。

The steady ___thrum of the engine filled the quiet workshop.