Answer:
The radius of circle is 10.5 units 
D is correct 
Explanation:
We are given a circle with centre M 
We need to find the radius of circle. 
Radius: It is distance from centre to a point on circle. 
In figure, 
Center at M 
Points on circle, R and S 
Radius should be RM, SM 
From figure, 
RM=10.5 units 
SM=10.5 units 
RM=SM=10.5 units 
Hence, The radius of circle is 10.5 units