Following up on yesterday's sixth year class, I thought I'd put this up.
Relative pronouns are quite tricky. They look and behave like articles. In a relative clause, they refer back to a noun in the previous clause. What's handy about them, is that because they behave and look like definite articles, they can hold all the grammatical information of the noun they refer to. If a noun is a subject, is masculine and is singular, then the relative pronoun with behave like a masculine, singular subject. Simples!
Remember that in a relative clause, the verb always goes to the end.
Click below to find a really good explanation of relative pronouns & clauses, with online exercises with which to practice.
Relative pronouns & Clauses: explanation and exercises