The ascent rate of _____ for diving is acceptable when using the NAUI dive tables.

The ascent rate of 30 feet per minute is considered acceptable when using the NAUI dive tables because it strikes a balance between safety and efficiency during a diver's ascent. Ascending too quickly can potentially lead to nitrogen narcosis or decompression sickness, commonly known as "the bends." The guidelines established within the NAUI (National Association of Underwater Instructors) framework emphasize a gradual ascent to allow nitrogen to safely eliminate from the diver's body.

At 30 feet per minute, this rate falls within a recommended limit that helps manage the body's decompression needs while still being manageable for most divers. It further provides sufficient time for safety stops, which are essential for deeper dives. The alternative options may not align with the standard safety protocols that NAUI has put in place. Ascending more slowly, such as 20 or 15 feet per minute, can be beneficial but is generally not necessary unless specified by certain dive conditions or individual diver circumstances. On the other hand, an ascent rate of 40 feet per minute exceeds the recommendations and could increase the risk of undesired effects from a rapid change in pressure.