空调发出持续的低沉嗡嗡声。

The air conditioner ___droned with a steady low hum.

会议期间，经理用单调的声音不停地说着数据，让人昏昏欲睡。

The manager kept ___droning on about the data during the meeting, making everyone sleepy.

农民用无人机喷洒农药。

The farmer uses a ___drone to spray pesticides.