Answer:
Option d. is correct
Explanation:
Given Points : 

We need to choose the most specific name for the polygon formed by points A, B and C .
Solution:
We know that a regular triangle is a polygon with three equal sides.
Also, for points 
 , distance is given by
, distance is given by 
 .
.

As AB = BC =AC, it's a regular triangle.
Option d. is correct