It wouldn't be A since 5 - 1 you would get 4 hundred not 4 tens. It wouldnt be B because 9 - 6 you would get 3 ones not 3 hundreds and 5-1 you would get 4 hundreds not 4 ones. It wouldnt be D because 9-6 would be 3 ones not 3 tens. Hope I helped ! Good luck !
x r (radius)