Which altitude trapped gas disorder occurs during ascent?

The correct choice highlights the significance of trapped gas disorders that can occur during ascent, particularly affecting the gastrointestinal (GI) tract and teeth. As an aircraft ascends, the decrease in atmospheric pressure can lead to the expansion of trapped gases in the body.

In the GI tract, gas that is normally present may expand due to the reduced external pressure, which can cause discomfort and even pain as it seeks to escape. Similarly, dental issues can arise if there are air pockets in or around the teeth or fillings; as the pressure decreases during ascent, this trapped air can lead to discomfort or pain.

That being said, while it is important to understand the mechanisms behind other options such as ear blockage, sinus pressure, and pneumothorax, these disorders pertain to other physiological systems and pressures. Ear blockage often occurs from the inability to equalize pressure in the eustachian tubes during ascent, sinus pressure relates to the sinuses and is impacted differently, and pneumothorax is a more serious condition involving the lung rather than the specific response of trapped gases due to ascent.