c
Magnetic field due to current carrying circular loop on its axis is given as
$\frac{\mu_0 ir ^2}{2\left( r ^2+ x ^2\right)^{3 / 2}}$
At centre, $x=0, B_1=\frac{\mu_0 i }{2 r }$
At $x=r, B_2=\frac{\mu_0 i}{2 \times 2 \sqrt{2 r}}$
$\frac{ B _1}{ B _2}=2 \sqrt{2}$