You put 399 into a saving account with an interest rate of 4% which earns $31.92 over a period of time how long was the period of time

Ithink the answer should be b.

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.