The second answer choice contains a vague pronoun reference. The pronoun it could refer to the windshield or the car.
The first answer choice shows a possible correction for the vague pronoun reference. It has been replaced with the car.
Scott washed the windshield of his car even though he knew the car would just get dirty again.
Which of the following contains a vague pronoun reference?
A: Scott washed the windshield of his car even though he knew it would just get dirty again.
B: Scott washed the windshield of his car even though he knew the car would just get dirty again.