The correct answer is option 4: zero.

When a man is sitting in a moving train, his speed with respect to the train is zero. This is because the man is not moving relative to the train. Since he is seated and not changing his position within the train, his speed is constant and remains at zero.

To understand this concept better, consider a scenario where you are sitting in a train that is moving at a constant velocity of 60 km/hour. If you were to look around you, you would see other objects inside the train, such as seats and fellow passengers, also moving at the same speed as you. This is because everyone and everything inside the train is moving together with the train itself.

It`s important to note that the man`s speed with respect to the ground is not zero. Since the train is moving, the man is also moving along with it. So, in the frame of reference of the ground, the man`s speed would be equal to the speed of the train, which is 60 km/hour.

In summary, the man`s speed with respect to the train is zero, but his speed with respect to the ground is 60 km/hour.