If the length of the longest chord of a certain circle is 20, what is the radius of that certain circle? Choose the correct answer
A) 2.5	B) 5	C) 10	D) 15	E) 20

Rationale: "longest chord of a circle is the diameter of the circle diameter = 2 * radius if diameter of the circle is given as 20 = 2 * 10 so radius of the circle = 10 correct answer - c"
Answer: C