Which of the following describes an example of a prohibited trap?

A full "S" trap is considered a prohibited trap because it creates a vertical rise followed by a horizontal run, which can lead to several plumbing problems. Specifically, this design can result in a trap that is too deep, risking the potential for siphoning, which can allow sewer gases to escape into the living space. Additionally, an "S" trap can maintain a water seal that is insufficient, leading to the trap emptying due to negative pressure or backpressure from the drainage system.

In contrast, the other types of traps mentioned, such as bell traps, crown vented traps, and separate fixture traps, typically either incorporate venting that helps maintain a proper water seal or are designed to prevent backflow and ensure the integrity of the trap seal. Therefore, the full "S" trap is specifically identified as a prohibited type due to its propensity to create sanitary and health issues within plumbing systems.