How many lines are marked on the hold short line of an instrument runway?

The correct answer reflects the standard marking for hold short lines on an instrument runway. A hold short line is specifically designed to indicate where an aircraft must stop to avoid entering an active runway or any area where it could interfere with the operations of other aircraft.

Two solid yellow lines are used for this purpose, positioned parallel to each other, with a specific distance between them. The solid lines serve to clearly delineate the point at which pilots must hold their aircraft while awaiting clearance for runway entry or crossing. This ensures safety by preventing unauthorized runway access which could lead to potential conflicts or accidents involving departing or landing aircraft.

In this context, the other options do not accurately represent the standardized marking system used for hold short lines, which are crucial for ground traffic management on an airport.