Final answer:
When you go up in an unpressurized airplane, your ears might pop due to the decreasing air pressure at higher altitudes. Pressure changes are responsible for sensations in the ears and are also a fundamental concept in explaining phenomena like buoyancy. The correct answer is option C.
Step-by-step explanation:
If you go up in an unpressurized airplane, you might feel your ears popping. This sensation is due to changes in air pressure as you gain altitude. The pressure of the atmosphere decreases as we climb higher, leading to an imbalance between the pressure in the middle ear and the external air pressure. The eustachian tubes in your ears open to equalize the pressure, which is when you may feel or hear the popping sensation. Similarly, underwater, pressure increases with depth, which can also affect your ears, but differently, often leading to a feeling of pressure or pain.
Pressure is a key concept in understanding various physical phenomena such as buoyancy, which allows ships to float and hot air balloons to rise. Changes in pressure underlie many everyday experiences and critical processes, from the discomfort you might feel in your ears during a flight or dive to the function of natural systems and engineering applications.