An electric field is applied to a semiconductor. Let the number of charge carriers be n and the average drift speed b v. If the temperature is increased.

If the temperature is increased, there will be more breaking of the Covalent bonds and more charge carriers are generated. This leads to total increase in moving charge carriers and thus their average drift speed will now be decrease due to increase in probability of collision with the lattice atoms of semiconductor. Hence number of charge carrier n will increase but the average drift speed v will decrease. Therefore, the correct answer is option B.

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