If a coil has diameter 'd', number of turns 'N' and form factor 'F' then the inductance of the coil is proportional to

A. \[{{\text{N}}^2}{\text{dF}}\]

B. \[{\text{N}}{{\text{d}}^2}{\text{F}}\]

C. \[\frac{{{{\text{N}}^2}{{\text{d}}^2}}}{{\text{F}}}\]

D. \[\frac{{{{\text{N}}^2}{\text{d}}}}{{\text{F}}}\]

Answer: Option C