What type of position indicators are commonly used to show that the landing gear is down and locked?

The correct answer is that a green light for each gear is commonly used to indicate that the landing gear is down and locked. This is based on aviation standards and practices where green lights serve as a positive indication that the landing gear is securely in place and ready for landing. The use of a green light provides a clear and immediate visual confirmation to the pilot that all gear components are correctly deployed and locked, which is crucial for safe landing operations.

Other options may represent different indicators or situations. For example, a red light typically signifies a fault or that the gear is not in a safe position, while a flashing orange light could indicate a transitional state or an alert requiring the pilot's attention. A single indicator panel light might combine multiple functions but does not offer the specific reassurance that individual green lights provide for each gear. Hence, the effectiveness and clarity of the green light system make it the standard choice for indicating that landing gear is down and locked.