What indication do you have that your aircraft might be experiencing icing issues?

When an aircraft experiences icing conditions, one of the most common indications is a feeling of sluggishness in the control surfaces. This is because ice accumulation can disrupt the airflow over the wings, ailerons, elevators, and rudder, leading to decreased aerodynamic efficiency. As the ice builds up, it changes the shape of the control surfaces, often increasing drag and altering the expected lift characteristics. Consequently, pilots may notice a lack of responsiveness and a need for more effort to achieve desired control inputs, making option C the most accurate indication of potential icing issues.

While other options could suggest various problems, they are not as directly linked to icing effects. For instance, a shiny appearance on the wings might indicate a layer of ice, but it isn't as immediate or actionable as a sluggish feel in control surfaces. An increase in drag can stem from various factors and doesn’t solely point to icing. Similarly, incorrect instrument readings could be due to instrument failure or other conditions unrelated to ice accumulation. Hence, the sensation of sluggishness in the control surfaces is a clear and immediate indicator of icing that pilots must recognize and respond to promptly.