同学你好，该知识点来自沪江网校《新概念英语2、3、4册连读【双11专享班】》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~
when the seeds are immersed in water
这里省略了the seeds are

状语从句同时具备下列两个条件:   ①主句和从句的主语一致，或从句主语为it；   ②从句主要动词是be的某种形式。从句中的主语和be动词常可省略。
When ( the museum is ) completed , the museum will be open to the public next year .
He’ll go to the seaside for his holiday if (it is ) possible.

祝同学学习进步~