Exercise 1: relative pronouns.
http://www.oup.com/elt/global/products/solutionsint/int_unit_page/unit3/grammar/exercise2
Exercise 2: relative pronouns; necessary or not?
http://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?10
Exercise 3: relative clauses; non defining.
http://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?12
Exercise 4: relative clauses; defining and non defining.
http://www.ego4u.com/en/cram-up/grammar/relative-clauses/exercises?07
