Final answer:
The relative clause in the sentence is 'whose car I borrowed', which provides additional information about 'the friend.' Proper use of pronouns is demonstrated in identifying subject and object pronouns in different clauses within a sentence.
Step-by-step explanation:
The relative clause in the sentence 'I'm making cookies for the friend whose car I borrowed' is 'whose car I borrowed'. This clause provides more information about 'the friend' and is therefore modifying that noun. The relative pronoun 'whose' indicates possession and relates back to the friend, explaining which friend is being referred to by specifying that the friend is the one owning the car that was borrowed.
The application of pronouns in sentences can be observed in examples like 'Antonio and I have occasional disagreements about the dishes', where 'I' is the subject personal pronoun, and 'disagreements about the dishes come up between Antonio and me', where 'me' is the objective case pronoun. It is important to choose the correct pronoun based on whether it is the subject or the object in a sentence.