Answer:
A. 6
Explanation:
We see that 20 is a diameter that goes through the center of the point. This means that the top half of the black line is 10 and the top half of the blue line is 8. Use the Pythagorean Theorem to find out the length of the shortest side by doing 10^2 - 8^2 = x^2. x^2 = 36; x = 6.