focus的複數形式

例句：

The discussion focused on three main problems.

討論集中在三個主要問題上。

Suddently the lights focused on the piano on the stage.

燈光突然聚焦在舞臺上的鋼琴上。

We need to shift the focus of this debate.

我們需要轉換一下辯論的焦點。