______________ can be used as backup buoyancy.

The correct answer highlights the use of both a dual bladder wing and a lift bag as backup buoyancy options.

A dual bladder wing is specifically designed for diving, providing buoyancy control during ascent and descent. It is especially beneficial in situations where a primary buoyancy device may fail, as having two bladders ensures that if one fails, the other can still provide adequate buoyancy.

A lift bag, on the other hand, is a specialized bag used to lift objects or provide buoyancy to a diver. It can be filled with air to provide additional buoyancy, acting as a reliable backup in scenarios where a diver may need to ascend quickly or if they are in distress.

By selecting both options, it encompasses various backup systems divers can rely on, enhancing safety during dives and allowing for quick responses to potential buoyancy failures. Each of these devices serves an important role in a diver's equipment repertoire, contributing to overall safety and control underwater.