Answer:
Option D.
Explanation:
A student used a compass and a straightedge to bisect angle ABC in the given figure. 
We need to find the statement that best describes point S. 
To bisect the angle ABC, the construction stps are: 
1. Place the compass on B and draw arc PQ. 
2. Now place the compass on P, then draw an arc. 
3. After-that without changing the compass, place the compass on Q, then draw an arc that intersect the arc at S. 
It means 
QS = PS 
Hence, the correct option is D.