In 'the man who came', 'who' is a relative pronoun and 'who came' is a relative clause.

在the man who came中，who是关系代词，而who came是关系从句。

Is a relative pronoun necessary here?

这里需要一个关系代词吗？

What is the relative pronoun in this clause?

这个从句里的关系代词是什么？

The relative pronoun is often dropped if it is the object.

关系代词作宾语时常被省略。

The relative pronoun is often dropped if it is the subject.

关系代名词做受词时常被省略。