Answer: C) scalene
======================================================
Step-by-step explanation:
Use the distance formula to calculate the distance from R to S. This is identical to the length of segment RS.

Segment RS is exactly 5 units long.
-----------------------
Repeat similar steps to find the length of segment ST

ST is roughly 4.2426 units long.
------------------------
Lastly, let's calculate the length of segment TR.

TR is about 6.0828 units long.
------------------------
Summary of the segment lengths:
- RS = 5 exactly
- ST = 4.2426 approximately
- TR = 6.0828 approximately
The three sides are different lengths.
Therefore, the triangle is scalene.