focus的复数形式

例句：

The discussion focused on three main problems.

讨论集中在三个主要问题上。

Suddently the lights focused on the piano on the stage.

灯光突然聚焦在舞台上的钢琴上。

We need to shift the focus of this debate.

我们需要转换一下辩论的焦点。