The girl and the dog that I saw on the beach are at home now.

Relative Pronouns – Pronomes Relativos

São palavras que se referem a termos mencionados anteriormente. Eles introduzem orações subordinadas adjetivas ( restritivas ou explicativas) e têm uma função dentro dessa oração ( Essas orações definem, limitam ou acrescentam algo ao significado do antecedente.).

São eles:

who (que, o qual, a qual, os quais, as quais, quem) e whom referem-se a pessoas;

The girl who I saw is beautiful.
The girl whom I saw is beautiful.

which ( que, o qual, a qual, os quais, as quais) refere-se a objetos e animais;

The dog which entered the room is sick.
The dog which you saw is sick.

That ( que, o qual, a qual, os quais, as quais) pode se referir a pessoas, objetos e animais.Não pode ser usado com preposição.

The girl that arrived is beautiful.
The girl that I saw is beautiful.
The dog that you saw is sick.

Whose ( cujo, cuja, cujos, cujas, de quem, do qual, da qual, dos quais, das quais)  indica a relação de posse, isto é, seu antecedente é sempre o possuidor.Não pode ser omitido.

That’s the girl whose car was stolen.
The car whose door is open is very old
I know the author whose stories you like.
I have the book whose stories you like.

NOTE: Sempre junto de um substantivo.

Como se empregam os pronomes relativos:

a) Sujeito da oração adjetiva

antecedente (pessoa) + who / that + verbo

antecedente (coisa ou animal) + which / that + verbo

The man who is at the door is Peter.
The man that is at the door is Peter.
The book which is on the table is mine.
The book that is on the table is mine.
The dog which is under the table is mine.
The dog that is under the table is mine.

b) Objeto direto

Usa-se whom quando o objeto se refere à pessoa ( inglês formal).Na língua falada usa-se who ou se omite o pronome relativo.

antecedente (pessoa) + whom / that / who + sujeito + verbo

antecedente (coisa ou animal) + which / that + sujeito + verbo

The man whom they admire is Peter. (formal)
The man who they admire is Peter. (informal)
The man that they admire is Peter. (informal)
The man they admire is Peter. (informal)
The book which they bought is a best-seller.
The book that they bought is a best-seller.
The book they bought is a best-seller.
The dog which they bought is a poodle.
The dog that they bought is a poodle.
The dog they bought is a poodle.

c) Objeto indireto

Usa-se whom e which precedidos de preposição (inglês formal).

antecedente (pessoa) + preposição + whom + sujeito + verbo

antecedente (coisa ou animal) + preposição + which + sujeito + verbo

The man to whom you spoke is Peter.
That is the street in which she lives.
The girl about whom you are talking is my niece.
The table on which you put your shoes cost 300 dollars.

Depois de preposição não se usa that .

NOTE:
Normalmente omite-se o pronome relativo e  desloca-se a preposição para depois do verbo ou, se o verbo estiver seguido de um objeto direto, para depois deste.

The man to whom you spoke is Peter. (formal)
The man you spoke to is Peter. (informal)

That’s the boy to whom I gave the book. (formal)
That’s the boy I gave the book to. (informal)

That is the street in which she lives. (formal)
That is the street she lives in. (informal)

That é o único pronome relativo usado após superlativos e palavras como: some, any, no, everything, much, little, only, all.

He is the best doctor that I know.
She is the only woman that loves you.

That também é o único pronome relativo usado quando há antecedentes diferentes.

The girl and the dog that I saw on the beach are at home now.