In what situation would you use carburetor heat?

Using carburetor heat is primarily aimed at preventing carburetor icing. This condition can occur in certain atmospherical conditions, particularly when the temperature is low and humidity is high. When air passes through the carburetor, it expands and cools, which can lead to ice formation if the conditions are right. This icing can restrict airflow to the engine and affect performance.

When carburetor heat is applied, it works by introducing warmer air into the carburetor, which helps melt any ice that has formed and prevents new ice from developing. This is particularly crucial during the phases of flight where these conditions are likely to be encountered, such as during climbs and descents in cooler temperatures or during flight at lower power settings where there is a higher likelihood of icing.

The other answer choices do not specifically address the main reason for using carburetor heat. While carburetor heat may be more relevant at lower altitudes where icing is more common, it is not required simply because one is flying at high altitudes or in rain, nor is it primarily related to engine starting procedures under normal conditions.