那只狗独自在房子里待了好几天。

The dog was in the house ___by ___itself for several days.

那只狗设法自己把箱子拖进了房间。

The dog managed to drag the box into the room ___by ___itself.

我没有吃任何咳嗽药——它自己就好了。

I didn't take any medicine for the cough - it just got better ___itself.