a

$\text{Magnetic field due to first loop is } B_1 = \frac{\mu_0I}{2r}$

$\text{when wire is bent in three loops current through one loop is }\frac{I}{3} \text{and its radius is  }\frac{r}{3}$

$\text{Magnetic field due to one of the three loops is } \frac{\mu_0I/3}{2r/3}$

$\text{Total Magnetic Field is } B_2 = \frac{3\mu_0 I}{2r}$

$\text{ Ratio of magnetic Field } B_1 :B_2 = 1:3$