Which of the following are types of elevators?

The correct answer highlights two widely recognized types of elevators: traction elevators and hydraulic elevators.

Traction elevators operate using a system of cables and pulleys. They rely on the principle of counterweight, where the weight of the cab is balanced by a counterweight, making them efficient for taller buildings. These elevators have hoisting machinery located at the top of the shaft and can travel at high speeds.

Hydraulic elevators, on the other hand, use a hydraulic system to lift the elevator car. A hydraulic piston pushes the car up from below. They tend to be more suitable for low-rise buildings, as their travel distance is generally limited compared to traction elevators. Hydraulic systems are generally quieter and smoother in operation for shorter distances.

While other options present different concepts related to elevators, they either refer to variations not typically classified as primary types or introduce terms not standard in elevator classification. Understanding these two main types helps in comprehending how elevators function and their appropriate applications in building design.