The magnet used in a magnetic compass is:
permanent magnet
Explanation of correct option:
(b) permanent magnet
Explanation of incorrect option:
(a) Electromagnet loses its magnetism as soon as the electric current is turned off so it cannot be used in a compass for navigation.
(c) Temporary magnets will lose their magnetism so these cannot be used in the compass for navigation.
Thus, the correct option is (b).