What conditions can lead to carburetor icing?

Carburetor icing occurs primarily when temperatures are low and humidity is high, making this the correct answer. In conditions of low temperatures, the carburetor's venturi effect causes the temperature of the fuel-air mixture to drop, which can result in moisture in the air condensing into ice. When the air is also humid, there is an increased amount of moisture present, which can lead to the formation of ice in the carburetor. This icing can disrupt the airflow and severely affect engine performance.

High temperatures and low humidity do not typically promote carburetor icing, as warmer air holds more moisture and the overall capacity to form ice is reduced. Similarly, cool temperatures and dry weather also do not provide the necessary humidity for ice formation. Although aircraft flying at high altitudes may encounter low temperatures, the altitude itself is not a direct factor that causes carburetor icing; rather, it's the combination of low temperatures and humidity that plays a crucial role in its formation.