The correct answer is option 'D', which states that the cam follower should move with cycloidal motion. This is the most suitable motion for high-speed engines. Let's understand why this is the case.

Cycloidal motion refers to the motion of a point on the circumference of a circle as it rolls along a straight line. In the case of a cam follower, the cam is a rotating component with an irregular shape (usually a cam profile) that imparts motion to the follower. The follower, in turn, transfers this motion to other components of the engine.

Now, let's discuss why cycloidal motion is preferred for high-speed engines:

1. Smooth and continuous motion: Cycloidal motion offers a smooth and continuous motion profile, which is essential for high-speed engines. This ensures that there are no sudden jerks or vibrations that could cause damage or reduce the efficiency of the engine.

2. Reduced friction and wear: The shape of the cam profile in a cycloidal motion mechanism allows for reduced friction and wear between the cam and the follower. This is important in high-speed engines where components experience higher loads and stresses. By minimizing friction and wear, the engine's lifespan can be extended, and maintenance costs can be reduced.

3. Minimized impact forces: Cycloidal motion helps to minimize impact forces between the cam and the follower. High-speed engines operate at high rotational speeds, and any sudden impact or shock can lead to component failure. The smooth and gradual motion provided by cycloidal motion reduces the impact forces, ensuring the longevity and reliability of the engine.

4. Efficient power transmission: Cycloidal motion facilitates efficient power transmission from the cam to the follower. This is crucial in high-speed engines where power needs to be transferred accurately and rapidly. The cycloidal motion ensures that the follower moves in a controlled manner, maximizing the power transmission efficiency.

5. Reduced noise and vibration: High-speed engines often generate significant noise and vibrations. The cycloidal motion helps in reducing these undesirable effects by providing a smoother motion. This leads to quieter engine operation and improved overall comfort.

Overall, the selection of cycloidal motion for high-speed engines is based on its ability to provide smooth and continuous motion, minimize friction and wear, reduce impact forces, facilitate efficient power transmission, and reduce noise and vibrations. These factors contribute to the optimal performance and longevity of the engine.