The most likely cause of buffering issues when moving outdoors is signal degradation. Wireless signals weaken as they travel through obstacles such as walls, glass, and air, leading to weaker connections and reduced data rates.

Breakdown of Options:

A. Network congestion – While congestion can slow down network speeds, it affects all users, not just those moving outdoors.

B. Wireless interference – Interference is possible but is more likely caused by other wireless signals rather than outdoor movement.

C. Signal degradation – Correct answer. Wireless signals weaken with distance and obstacles such as walls, reducing performance.

D. Client disassociation – Disassociation occurs when clients lose connection to the AP, but the question states that users experience buffering, indicating they are still connected but with a weak signal.