Mean Free Path: the Mean Free Path of an Oxygen

Mean free path: The mean free path of an oxygen molecule is 2.0 × 10^-5 m, when the gas is at a pressure of 120 Pa and a temperature of 275 K. The atomic mass of oxygen is 16.0 g/mol, the Boltzmann constant is 1.38 × 10^-23 J/K, Avogadro's number is 6.02 × 10²³ molecules/mole, and the ideal gas constant is J/mol ∙ K = 0.0821 L ∙ atm/mol ∙ K. The radius of an oxygen molecule is closest to

A) 0.22 nm.
B) 0.24 nm.
C) 0.26 nm.
D) 0.28 nm.
E) 0.30 nm.