What types of ignition system are commonly used on gas turbine engines?

The correct choice indicates that gas turbine engines commonly utilize high intensity, intermittent duty capacity ignition systems. This type of ignition system is designed to provide a reliable and robust spark necessary to initiate combustion in the engine's combustion chamber. High intensity refers to the strong electrical discharge produced, which is crucial for igniting fuel-air mixtures, especially in conditions that may be challenging for combustion to initiate.

The intermittent duty capacity aspect is important because it reflects how the ignition system operates only during specific phases of the engine operation, such as starting or during abnormal conditions where re-ignition is necessary. This feature helps in maintaining the efficiency and operational integrity of the gas turbine, as the ignition system does not have to be active at all times, reducing wear and improving reliability.

Contextually, other options do not reflect the operational requirements of gas turbine ignition systems. For example, low intensity ignition might not produce a sufficient spark to ignite the fuel-air mixture effectively, especially under the higher pressure conditions found within gas turbines. Similarly, high AC and low DC systems might refer to electrical systems unrelated to the combustion requirements of gas turbines. Thus, the choice of a high intensity system with intermittent duty aligns perfectly with the demands of efficient and reliable engine operation.