What is one of the prerequisites for squeeze to occur during descent?

Squeeze occurs during descent when the pressure surrounding a gas-filled space increases, which can lead to the compression of that space if it is not able to equalize with the surrounding pressure change. For squeeze to take place, there needs to be an existing gas-filled space within the body or adjacent to it that cannot equalize in pressure effectively. This prerequisite is fundamental because, without a gas-filled space, there is no volume of gas to be affected by the increasing external pressure.

When divers descend, the ambient pressure increases, and if a gas-filled cavity, like those in the sinuses, lungs, or other body spaces, cannot adapt to the changing pressure, the walls enclosing that gas may collapse, causing pain or injury. This makes the presence of a gas-filled space crucial for the phenomenon of squeeze to happen. The other options do not capture this essential requirement clearly, as they either suggest conditions that are not necessary for squeeze or misrepresent how gas behavior functions under pressure changes.