Which of the following describes one method of anti-icing in aircraft?

The method described involves activating carburetor heat, which is critical for preventing ice formation in the carburetor system of an aircraft. This is particularly important in conditions where the temperature is at or below freezing and humidity is high. When the carburetor heat is activated, the warm air from the engine is directed into the carburetor, raising its temperature and preventing the formation of ice. Carburetor icing can lead to power loss and engine performance issues, so this is a vital procedure during flight operation under specific atmospheric conditions.

The other options serve different purposes: using chemical de-icers applies to external surfaces or components, external heating blankets may relate to the overall heating of the aircraft in extreme cold conditions, and engaging the autopilot system does not directly pertain to ice prevention but focuses on maintaining aircraft control. Understanding these distinctions highlights the importance of the correct application of anti-icing measures during specific conditions.