Radius = 5.1
Diameter = 10.2
Step-by-step explanation:
Radius is a straight line that connects the center of a circle to a point on the circumference (outside of the circle).
Diameter is a straight line that goes through the center of a circle and connects two points on the circumference (outside of the circle).
The line shown goes from the center to the outside of the circle, so it is the radius