A student claims that only one operation is needed to calculate the length of the subtended arc when given the measure of a central angle in radians and the diameter of the circle. Which option supports the student's claim?

Having the angle in radians and the diameter of the circle we can easily calculate the length using the followingexpression

Length = angle (radians) * diameter/2

With this expression we can easily deduce the perimeter of a circle (length of the full arc)

Length = Perimeter = 2*pi*r

There is only one operation involved in this process