同学你好，该知识点来自沪江网校《Hitalk口语【外教1V1】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学好，
She's the one wearing a dress. 相当于She's the one (who is) wearing a dress.
wearing分词是从定语从句演变而来的。

在这几个句子里，in + 名词，表示穿什么，也可以用in+颜色名词，如in red, in black。

He is the one in white pants.  这就是主系表为主干的句子，in white pants是介宾结构修饰。

She is very attractive in that purple dress. in that purple dress也是介宾修饰。

学习愉快！