What is the major operational difference between traction and hydraulic elevators?

The correct answer highlights the fundamental operational mechanism that distinguishes traction elevators from hydraulic elevators. Traction elevators operate by using cables and pulleys to lift the elevator car, which are controlled by an electric motor. The presence of these cables allows for smooth and efficient vertical movement and enables traction elevators to travel at higher speeds and greater heights.

On the other hand, hydraulic elevators function by employing a fluid-driven piston, which pushes the elevator car upwards. This plunger mechanism causes the elevator to move vertically by using hydraulic fluids, which generally limits how high they can travel compared to traction elevators due to the physical constraints of the hydraulic system and the need for a machine room to house the hydraulic components.

Understanding this distinction clarifies how each type of elevator operates, thus making B the correct choice due to its accurate representation of the operational differences.