that is a/an造句

Most authorities agree that play is an essential part of a child's development.

大多数权威人士认为玩耍是孩子成长的一个重要部分。

This is a citywide problem that has to be addressed as an emergency.

这是个全城性的问题，必须当做紧急事件对待。

An illustration of China's dynamism is that a new company is formed in Shanghai every 11 seconds.

说明中国活力的一个实例便是在上海每11秒钟就有一家新公司成立。

A proton is an elementary particle of matter that possesses a positive charge.

质子是带正电荷的物质的基本粒子。

I've found a vase that is an exact match of the one I broke.

我找到了一只花瓶，和我打碎的那个一模一样。

that is a/an造句

And that is a preface to an idea of computational complexity we're going to come back to.