To simplify a ratio, first make into the fraction form. a:b =

Then find the prime factors of both the numerator and denominator.

Now cancel out any common factors. But if there isn't any common factors, then the fraction or ratio is in its simplest formula.
And that is the case here.
And because the question wants the answer in ratio form, make the fraction back into a ratio.
So, A. 15:37 is the answer.