The correct answer is option 1, stretching of the tympanic membrane. During take-off or landing of an aircraft, the change in altitude causes a rapid change in air pressure. This sudden change in pressure can affect the middle ear, which is connected to the back of the throat by a small tube called the Eustachian tube. The Eustachian tube helps equalize the pressure inside the middle ear with the pressure outside.

When the pressure changes rapidly, as it does during take-off or landing, the Eustachian tube may not be able to equalize the pressure quickly enough. This can cause a difference in pressure between the middle ear and the outside environment, which can put strain on the tympanic membrane, commonly known as the eardrum. The stretching of the tympanic membrane can lead to discomfort or even pain in the ears.

Options 2, 3, and 4 are not correct in this context. Damage to the middle ear ossicles, increased impulses to the cochlea, and vibrations in the bony labyrinth of the inner ear are not directly linked to the discomfort or pain experienced during take-off or landing.