If an obstacle cannot be avoided and you must drive over it, at what angle should you approach it?

Answer: D — 90-degree angle

When approaching an obstacle that cannot be avoided and you must drive over it, the correct angle to approach it is a 90-degree angle. Approaching the obstacle at a 90-degree angle helps to minimize the impact and reduces the chances of losing control of the motorcycle. This approach allows for a smoother transition over the obstacle, maintaining stability and control of the motorcycle. The other angles listed in the options would not provide the same level of control and safety when navigating over an obstacle on a motorcycle.