Which of the following is a common feature found in all buoyancy control devices?

A common feature found in all buoyancy control devices (BCDs) is an overpressure relief valve. This component is crucial for regulating the internal pressure of the BCD as a diver ascends and descends. When a diver ascends, the air inside the BCD expands due to the decrease in external pressure. If the internal pressure becomes too high, it can lead to damage or failure of the BCD. The overpressure relief valve prevents such situations by allowing excess air to escape when the pressure threshold is reached, ensuring the integrity and safety of the BCD during use.

While adjustable buoyancy is a key function of BCDs, it is not a physical component like the overpressure relief valve. Similarly, a pressure gauge, though useful for monitoring the diver's air supply, is not a standard feature of all BCDs. Built-in weights serve a different purpose and are not found in every buoyancy control device. Thus, the overpressure relief valve stands out as a necessary safety feature that enhances the overall functionality and reliability of buoyancy control devices for scuba divers.