What are the two main purposes of pressurizing aircraft cabins?

Pressurizing aircraft cabins serves two primary functions that are crucial for safe and comfortable flight operations. First, it creates a controlled and breathable environment for passengers and crew at high altitudes where the outside atmosphere is insufficient for human survival. At cruising altitudes, the external air pressure is dangerously low, which is why pressurization is necessary to maintain an appropriate oxygen level and provide breathable air.

Second, pressurizing the cabin enables aircraft to operate effectively at high altitudes, where air density is lower. Flying at these altitudes reduces aerodynamic drag, allowing for better fuel efficiency and enhanced performance. Therefore, the combination of ensuring breathable air and facilitating safe flight operations at high elevations is essential for modern aviation, making the option highlighting these benefits correct.