同学你好，该知识点来自沪江网校《【Uni智能】托福签95冲105名师VIP签约-高中起点【现金奖励班】》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。

同学你好~
助助查了下这个句子的来源应该是一篇文章的标题，原标题是Desert plant seen drinking fog and mist with its leaves
在英语中，被动语态陈述句作标题时，有时会省略掉被动语态中的助动词be
例如：More than 10 people were killed in the earthquake
做标题时会缩减为：More than 10 (people were) killed in (the) earthquake

同学的句子这里是seen前省略掉了was，实际应该是was seen drinking被看到正在喝
用到了see doing，表示看见正在做

祝学习愉快~