Find the exact circumference of circle o.

The formula for the circumference of a circle is 

C=πd   where d=diameter

The line segment AC would be the diameter of the circle, but in order to solve for it, since its the hypotenuse of a right triangle, we need to use the pythagorean theorem.

a²+b²=c²
6²+8²=c²
36+64=c²
100=c²
√100=c
10=c

So line segment AC is 10 units long. The diameter is 10 units long. Now we can solve for the circumference

C=πd
C=10π

Since they asked for the EXACT circumference, we can stop here. 

Answer=10π

Yes i also think it is b