Which of the following methods CANNOT be used to produce a steel magnet? The

A.

passing of an electric current through a solenoid

B.

repeated stroking of the specimen with a magnet

C.

repeated stroking of the specimen in opposite directions with magnets

D.

heating of the specimen

E.

hammering of the specimen in the earth's magnetic field

Correct answer is D

No explanation has been provided for this answer.