◾The relative pronouns take the place of nouns and pronouns;and they are used to join two sentences about the same person or thing.
◾Examples of relative pronouns are who,which,that,whom and whose.
◾We use whom to make a statement about human beings.
◾It is used in place of who
(a)when it is the object of a verb or
(b)when it comes after a preposition.