同学你好，该知识点来自沪江网校《大学水平直达托福105分【随到随学班】》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，解答如下，希望能帮到你：
First came the cats, which were used on ships to control rats.
主句是First came the cats，从句是which were used on ships to control rats.
主语在主句中，找到名词成分，cats，答案就出来了。

Then came the rabbits, which were ……
主句是Then came the rabbits，从句是which were ……
主语在主句中，找到名词成分，rabbits，答案就出来了。