If you think it can be useful for you watch a video tutorial about the relative clauses.
Then, put theory into practice by doing some exercises.
- Exercise 1A & Exercise 1B on relative pronouns
- Exercise 2A & Exercise 2B on subject or object relative pronouns
- Exercise 3 on relative adverbs
- Exercise 3A & Exercise 3B on the formation of relative clauses
- Exercise 4 on the formation of relative clauses without the relative pronoun
- Exercise 5
Finally, test yourself.