A cylindrical conductor of radius R is carrying a constant current....

Inside $( d < R )$

Magnetic field inside conductor

$B = Kd . . ( i )$

This is straight line passing through origin

At surface $( d = R )$

$B = \dfrac{{\mu}_{0}}{2\pi}\dfrac{1}{d}$

Maximum at surface

Outside $( d > R )$

$B = \dfrac{{\mu}_{0}}{2\pi}\dfrac{1}{d}$

or $B ∝ \dfrac{1}{d}$ $∴$ Hyperbolic

Hence the correct option is (B)