A coterminal angle is one that is shares the same side that makes an angle. Since they are asking for a POSITIVE angle, we simply rotate another full rotation (360 degrees or 2pi rads) to get to the same side again.
Thus, 11pi/7 + 2pi = 11pi/7 + 14pi/7 = 25pi/7
The answer is the last one.
7/4/2014

Michael A.