Since the two circles are identical, the two lengths below (indicated by x) are the same length.
Let's also let y = the length of AB

Since we're told $O_1O_2=9$, we can write: x + y + x = 9
Since we're told AB=3, we can write: x + 3 + x = 9
Solve to get x = 3


So the individual lengths are as follows:




This means we can calculate the radius of the circle centered at $O_1$

The radius = 3 + 3 = 6

Circumference of circle = 2πr = 2π(6) = 12π

Answer: C

Cheers,
Brent