Answer:
D. 10
Explanation:
The chord is bisected as shown by the perpendicular lines and right angle, so both segments are 6.
Draw a radius from the center to the end of the chord to create a right triangle. 8 and 6 are the legs, use pythagorean theorem to find the length of the segment you drew because its the hypotenuse.
8^2+6^2=x^2
64+36
100
square root of 100 is 10
So, 10 is the length of the segment. Both the x segment and the 10 segment are radii because they are draw from the center to a point on the circle.
They are equal.
x=10