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a) As we know that the drift velocity depends on the current as,

Where n is the no. of charge carriers per unit volume, e is the charge of an electron, I is the current flowing and A is the area of cross section of the resistance.

As we know that,

n_metals>n_{semiconductors}

so, for the same value of current and same area of cross-section the drift velocity of electrons in metal resistance is smaller than in the n-type semiconductor.

b) If the same constant current continues to flow for a long time, the voltage drop across A will increase as the resistance of metal increases with increase in temperature but will decrease in B as the resistance of a semiconductor decreases with increase in temperature.