What should you do when you brake hard on a straightaway and your rear brake locks?

Answer: D — Continue braking until the motorcycle stops

When you brake hard on a straightaway and your rear brake locks, the appropriate action is to release the rear brake. Continuing to brake means that you would not regain control, as a locked rear brake can cause you to lose traction and lead to a skid. By releasing the rear brake, you allow the rear wheel to start rotating again, which helps to regain traction and control of the motorcycle. This is crucial in preventing a loss of balance and steering capability. It is essential to manage the braking process by applying gradual pressure rather than hard braking, especially in situations where traction is compromised. In contrast, pulling the kill switch or accelerating would not help the situation and could instead lead to more dangerous outcomes due to loss of control. Understanding this technique can significantly enhance the rider's safety and control on the road.