Runway threshold is indicated by a series of parallel lines starting from a distance of A. 3 m from runway end B. 6 m from runway end C. 10 m from runway end D. 15 m from runway end

The correct answer is: C. 10 m from runway end

Runway threshold is indicated by a series of parallel lines, called threshold markings, starting from a distance of 10 m from the runway end. These lines are white and are 30 cm wide. They are located on the centerline of the runway and extend across the width of the runway.

The threshold markings serve as a visual reference for pilots to determine when they have reached the beginning of the runway. They also help to prevent pilots from landing short of the runway, which can be dangerous.

The threshold markings are one of the many safety features that are found on runways. These features help to ensure that pilots can land safely and avoid accidents.

The other options are incorrect because they are not the correct distance from the runway end at which the threshold markings are located.