Reduced Relative Clauses
You may delete the relative pronoun (who, that, which) and the “be” verb when:
1. they are followed by a prepositional phrase.
A. The man who is in the house likes to watch television all day.
B. The books that are on the desk are mine.
2. the main verb in the relative clause is progressive.
A. The man who is swimming in the lake is my father.
B. The clothes that are lying on the floor belong to me.
3. the main verb in the relative clause is passive.
A. The survey which was conducted by the government did not indicate true public opinion.
B. The food that was eaten by the mice was poisonous.