Choose the correct alternatives :
(a) Alloys of metals usually have (greater/less) resistivity than that of their constituent metals.
(b) Alloys usually have much (lower/higher) temperature coefficients of resistance than pure metals.
(c ) The resistivity of the alloy manganin in (nearly independent of/ increase rapidly ) with increase of temperature.
(d) 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) or 10^(23))`.

Explanation

(a) Alloys of metal usually have greater resistivity than that of their constituent metals
(b) Alloys usually have lower temperature coefficients of resistance than pure metals
(c) The resistivity of the alloy, manganin, is nearly independent of increase of temperature
(d) The resistivity of a typical insulator is greater than that of a metal by a factor of the order of `10^(22)`.