Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors:

(a) number of charge carriers can change with temperature T.

(b) time interval between two successive collisions can depend on T.

(c) length of material can be a function of T.

(d) mass of carriers is a function of T.

Which are the correct options? 

(a), (b)

We know that resistivity ( ρ ) depends on mass of charge-carrier (m), relaxation time ( τ ). Length and mass cannot be function of T as the mass of a body is constant everywhere. Length of body changes negligibly with temperature. As τ decreases on increasing T due to the rise in the speed of change-carriers and n increases on increasing temperature. So it will affect the ρ or ρ is the function of T.