Answer:
C. R is the midpoint of PQ.
Explanation:
Given that segment PQ is bisected at point R by MN.
It means PQ is divided into two parts at point R by the segment MN.
That is, PR = RQ
Hence, R is the midpoint of PQ.
It is not given that the segment MN is bisected by PQ.
So, R need not be the midpoint of MN.
Please refer to the attached figure for better understanding.