The mean free path for a gas, with molecular diameter \(d\) and number density \(n\) can be expressed as :
A \(\frac{1}{\sqrt{2} n \pi d}\)
(B) \(\frac{1}{\sqrt{2} n \pi d^{2}}\)
C \(\frac{1}{\sqrt{2} n^{2} \pi d^{2}}\)
D \(\frac{1}{\sqrt{2} n^{2} \pi^{2} d^{2}}\)