Within how many inches should you park parallel to the curb in Washington State?

Answer: C — 12 inches

In Washington State, the law states that when parallel parking, you must be within 12 inches of the sidewalk or curb. This allows enough space for pedestrians to walk along the sidewalk and for other vehicles to pass by safely. Options A and B (6 inches and 9 inches) are too close to the curb and may impede the flow of traffic or cause potential damage to your car's wheels. Option D (18 inches) is too far from the curb and could also lead to hindrances for other cars. Therefore, the correct distance for parallel parking in Washington State is 12 inches.