drone的第三人称单数形式

　　例句：

　　A plane was droning in the distance.

　　飞机在远处嗡嗡地响。

　　The drone of the engine made her sleepy.

　　发动机的嗡嗡声使她困倦。

　　Outside the tent I could hear the constant drone of flies.

　　我能够听到帐篷外面苍蝇不断的嗡嗡声。