Maximum straight line braking is achieved by:

Answer: D — Applying both brakes without the wheels locking

Maximum straight line braking is achieved by applying both brakes without locking the wheels. When you apply both the front and rear brakes simultaneously, you distribute the braking force evenly, allowing for more efficient and controlled braking. Locking the wheels can lead to loss of traction and control, so it is essential to modulate the brakes to prevent this. Therefore, applying both brakes without locking the wheels is the correct choice for achieving maximum straight line braking.