As per the question the diagram given is a vertical line.
We are asked to calculate the position of X.
Here the vertical line is divided into many segments.
As per the diagram, it is obvious that the points marked at different positions are separated by four units from each other i.e the distance between two successive marks is 4 units.
The point X is situated at four marks away from 0.
Hence the position of X will be= 4×4 units
= 16 units
Hence the correct answer of this question is D.