The correct response is: So that your employer does not hold out too much or too little in taxes.
Filling out the W-4 form correctly is important because it provides your employer with the necessary information to withhold the appropriate amount of federal income tax from your paycheck. Incorrect information can lead to either over-withholding (resulting in a smaller paycheck and a potential tax refund when you file your tax return) or under-withholding (which could lead to owing a significant amount of tax at the end of the year).