有一下两个题干部分

Nancy is the only one of the visitors that is able to do that.

He is the only one of the foreign experts who is working in China.

请问老师是不是在这种情况下，不一定只能用that，我可以这样理解这种现象么？

谢谢老师。

回答如下：

你的问题可以归纳为以下2点来回答

【1】当先行词被the only, the same ,the very, the last, the best以及the +序数词修饰时，用关系代词that引导定语从句。

This is the same pen that I lost yester.

This is the right pen that I bought yesterday.

【2】当先行词 被of 介词短语修饰现实，即the one /one +of+限定词+名词复数时，如果名词是为表示人的名词，则用who,如果表示事物的名词，则用that

This is one of the pens that I bought yesterday.（先行词为表示物的名词，关系代词用that）

She is one of the persons who can speak English.（先行词为表示人的名词关系代词用who）

A. the only one of 限定词+名词复数，其关系代词所代替的先行词为the only one,因此其定语从句谓语用单数

He is the only one of the persons who is from  China.

B. one of 限定词+名词复数，其关系代词所代替的先行词为介词of后面名词复数,因此其定语从句谓语用复数数

She is one of the persons who are from China.