Which best describes how to find the length of an arc in a circle

The answer is C: Divide the arc's degree measure by 360°, then multiply by the circumference of the circle.

Explanation.
Let r =  radius of the circle
Then the circumference is C = 2πr.

Let the degree measure of the arc be x degrees.
In radians, the angle is (x/180)π radians
The measure of the arc is
r*(x/180)π = (x/180)*πr
                = (2x/360)*πr
                = (x360)*2πr
                = (x/360)*C

This proves the statement for the answer because
    x/360 is the degree measure divided by 360,
    C is the circumference.