Refer to figure. 
SOMATOGRAVIC ILLUSION

Somatogravic illusion is a perceptual phenomenon experienced by pilots during flight, particularly during acceleration or deceleration phases. It occurs due to the sensory organs in the inner ear (specifically the otolith organs) sensing linear accelerations and decelerations. These organs are responsible for detecting changes in head position relative to gravity.

When an aircraft accelerates forward (increases speed) or decelerates (decreases speed), the otolith organs may interpret these changes in linear acceleration as changes in pitch angle (nose-up or nose-down attitude). As a result, pilots may experience the sensation that the aircraft is pitching up (climbing) during acceleration or pitching down (descending) during deceleration, even though the actual flight path remains straight and level.

• Acceleration → Climb illusion 
• Deceleration → Descent illusion

When the aircraft is entering a turn, positive “g” acceleration is experienced which may lead to a climb illusion.

Let's analyze the given options:

Turning in the opposite direction → INCORRECT. This illusion might occur when rolling out of a turn, not when entering a turn.

Flying inverted → INCORRECT. Flying inverted (upside down) typically results in negative g. This sensation cannot occur when positive “g” acceleration increases.

Descending → INCORRECT. This illusion is experienced when the aircraft is decelerating, so when the positive “g” acceleration decreases.

Climbing → CORRECT. This illusion is experienced when the aircraft is accelerating (positive “g” acceleration increases during a turn).