Choose the correct alternative.
(I) Alloys of metals usually have greater resistivity than that of their constituent metals
(II) Alloys usually have much lower temperatue coefficients of resistance than pure metals
(III) The resistivity of the alloy manganin is nearly independent of temperature
(IV) The resistivity of a typical insulator (e.g., amber) is greater than that of a metal by a factor of the order of  ${10}^{22}$