During which phase does cabin pressurization increase?

The correct answer is during takeoff because this is the phase when cabin pressurization begins to increase substantially. As the aircraft ascends, the cabin pressure is gradually adjusted to maintain a comfortable environment for passengers and crew. The aircraft is designed to pressurize the cabin effectively during this ascent to ensure that the atmospheric conditions inside remain safe and pleasant, despite the decreasing external air pressure at higher altitudes.

Other phases do involve changes in cabin pressurization, but the most significant increase occurs during takeoff as the aircraft climbs to cruising altitude. While cruising, the cabin pressure is maintained at a constant level, and during landing, the pressure decreases gradually. When the aircraft is on the ground, the cabin pressure is typically at the same level as the external atmosphere, requiring that effective cabin pressurization is not needed until takeoff.