Relative Clauses

These words always refer to something or someone mentioned before in the same sentence.

Where refers to places.

Who refers to people.

Whom is more formal than who. (a quem)

Which and that refer to objects or animals.

Whose is used to express possession.


e.g. For teenagers appearance is something which comes first.
Over here, which refers to appearance.

The sentence above is defining relative clause. They are essential to the understanding of the context.

You can omit “who”, “that”, “which”, in defining relative clauses but only when they are the object.

e.g. That’s the CD (which, that) my boyfriend gave me.

In defining relative clauses when it’s an informal situation "that" can replace "who" or "which".

Whose

e.g. John, whose girlfriend is Simone, has stopped smoking.

When we add extra information in a sentence, we put it between commas and call it non-defining relative clause.
Who

e.g. Tom, who is allergic to smoke, is my neighbour.

In this sentence, the important information is that Tom is her neighbour. The information that Tom is allergic is something the speaker wanted to share.

Have a look at this link and complete the blanks of the exercise:
http://www.englisch-hilfen.de/en/exercises/pronouns/relative_pronouns2.htm