Relative clauses

Do you need to revise relative clauses?
Here you've got some online activities.

http://www.perfect-english-grammar.com/relative-clauses-exercise-1.html
http://www.englisch-hilfen.de/en/exercises/pronouns/relative_pronouns.htm
https://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?07
http://www.myenglishpages.com/site_php_files/grammar-exercise-relative-clauses.php
http://speakspeak.com/english-grammar-exercises/intermediate/relative-pronouns-who-which-that-whose-when-where