The correct answer is A. 30 meters.
The banner flag and stop indicator are used to warn drivers of upcoming construction work. The banner flag is typically placed 30 meters before the stop indicator, which is placed at the beginning of the construction zone. This distance is necessary to give drivers time to slow down and stop safely.
Option B is incorrect because it is the distance between the banner flag and the end of the construction zone. Option C is incorrect because it is the distance between the stop indicator and the end of the construction zone. Option D is incorrect because it is a much greater distance than is necessary to warn drivers of upcoming construction work.