The correct answer is A. 4.27 m.
The formation width for a single line meter gauge track in embankment as adopted on Indian Railways is 4.27 m. This includes the width of the track itself, which is 1.00 m, as well as the width of the ballast bed, which is 3.27 m. The ballast bed is a layer of crushed stone that provides support for the track and helps to drain water away from the track.
The formation width is important because it ensures that there is enough space for the track to be laid and maintained properly. It also helps to prevent the track from being damaged by flooding or other environmental factors.
The other options are incorrect because they do not represent the actual formation width for a single line meter gauge track in embankment as adopted on Indian Railways.