In Instrumental landing system, the middle markers are located A. Along the extended centre line of runway end B. About 1 km. ahead of the runway threshold C. At the runway threshold D. About 7 km. ahead of the runway threshold

The correct answer is: A. Along the extended centre line of runway end.

The middle marker is a visual aid in instrument landing systems (ILS) that is located along the extended center line of the runway end. It is typically a pair of white lights that are spaced 150 feet apart and are 100 feet above the ground. The middle marker is used by pilots to align their aircraft with the runway center line during final approach.

The other options are incorrect because:

• Option B is the location of the glide slope indicator.
• Option C is the location of the threshold marker.
• Option D is the location of the outer marker.