Which of the following places uses vacuum toilets?

The correct answer is option 3. Aeroplanes.

The "vacuum toilets" on airplanes are a unique kind of toilet. Therefore, sewage or human excreta are disposed of by vacuum toilets on airplanes. A valve in a vacuum-filled pipeline opens when we flush the toilet in an airplane. Human waste is removed off the toilet seat with enormous force and a loud noise by the vacuum in the pipeline, which then transports it to a tank within the aircraft. The tank containing all the human waste is dumped into a sewage line beneath the ground through connected pipes as soon as the plane touches down at an airport.