Which of the following best describes a traction elevator?

A traction elevator is characterized by its use of ropes and pulleys for movement, which is a key aspect of its operation. In this system, the elevator car is raised and lowered by a motor that turns a sheave (a type of pulley). The ropes are looped over the sheave and attached to the elevator car, allowing it to move efficiently both upwards and downwards. This mechanism provides smooth and reliable movement and is well-suited for taller buildings due to its ability to travel greater distances without losing performance.

The other options present alternative mechanisms and characteristics that do not apply to traction elevators. For example, hydraulic elevators operate on hydraulic pressure and do not utilize ropes or pulleys. Additionally, traction elevators are designed to carry heavy loads, making them ideal for commercial and high-rise applications, which contrasts with the claim that they cannot carry heavy loads. Lastly, while some modern traction elevators are designed to operate without traditional machine rooms, the essential characteristic of the traction system's operation relies on its rope and pulley system, distinguishing it from the options provided.