Chain survey is mainly done using triangulation technique because:

triangles reduce the error by 30%

a triangle is the only simple figure that can be plotted from the length of its sides measured in field

it is needed to form a well-conditioned triangle

in triangulation, the survey work can be checked using check line

Solution

Correct option is B

Chain Survey:
The principle of chain surveying is triangulation.
This means that the area to be surveyed is divided into a number of small triangles because the triangle is a simple figure that can be plotted from the length of its sides.
In chain surveying, the sides of the triangles are measured directly on the field by chain or tape, and no angular measurements are taken.