Which of the following could indicate wake turbulence?

Wake turbulence is a phenomenon that can affect an aircraft flying in the vicinity of another, particularly when following a larger aircraft. This turbulence results from the vortices generated by an aircraft's wingtips, which can persist in the air for some time after the aircraft has passed.

Unexpected yaw or roll is a clear indicator of wake turbulence because when an aircraft encounters these air currents, it can experience sudden and unanticipated lateral movements. This can manifest as a noticeable change in the aircraft's bank angle or yawing motion, which pilots must be prepared to manage. This response is particularly critical for smaller aircraft operating near or below larger aircraft, as they are more susceptible to the effects of wake turbulence.

In contrast, sudden altitude changes, changes in throttle response, and aircraft stalls or pitch fluctuations can be attributed to a variety of factors, not exclusively wake turbulence. Altitude changes may occur during normal flight maneuvers or turbulence unrelated to the wake of another aircraft. Changes in throttle response could stem from engine performance fluctuations, and stalls or pitch variations can arise from inappropriate control inputs or other aerodynamic issues. Thus, while these phenomena could indicate other flight dynamics, unexpected yaw or roll is specifically associated with the presence of wake turbulence.