Whose car is that (that) your mom is driving to get to the mall by 1pm?Whose stands for a possessive noun or pronoun:
Whose is that car?
Who(m) that car belongs to?
To Whom does that car belong?
Ex: Whose car? John's car. <possessive noun>______________
Ex: Whose car? His car. <possessive pronoun>
Could you shed some light on this?
Interested in Language