"One radian is defined to be the angle subtended where the arc length "S" is exactly equal to the?"

"One radian is defined to be the angle subtended where the arc length

1.	"One radian is defined to be the angle subtended where the arc length "S" is exactly equal to the?"
A.	radius of the circle.
B.	circumference of the circle.
C.	diameter of the circle.
D.	half of radius of the circle.
Answer» B. circumference of the circle.