We need to get always a repeating decimal, then:
A . 1/6 = 0.1666666 but 3/6 = 0.5 not a repeating decimal
B. 1/15 = 0.066666 but 3/15 = 0.2 not a repeating decimal
C. 1/18 = 0.055555 but 9/18 = 0.5 not a repeating decimal
D. 1/11 = 0.090909 , 3/11 = 0.27272727, 7/11 = 0.636363 and 10/11 = 0.909090
The right answer is D. 11
