Which one of the following ratio gives the purity of the metal (rho-resistivity (or) specific resistance)

Which one of the following ratio gives the purity of the metal (rho-re

1.	Which one of the following ratio gives the purity of the metal (rho-resistivity (or) specific resistance)
Answer» `(rho_(300^(@)C))/(rho_(4.2^(@)C))` `(rho_(300k))/(rho_(4.2K))` `(rho_(27k))/(rho_(4K))` `(rho_(300k))/(rho_(4^(@)C))` Answer :2