only

这是我唯一的玩具。

This is my ___only toy.

我是火车上唯一的人。

I was the ___only person on the train.

我只有十块钱。

I have ___only ten dollars.

我半小时前才到。

I ___only arrived half an hour ago.

我只是在开玩笑。

I was ___only joking.