N-type semiconductor is obtained by doping silicon with:

Correct option is A

1. An N-type semiconductor is formed by doping silicon (a tetravalent element) with a pentavalent impurity such as phosphorus, arsenic, or antimony.
2. These pentavalent impurities introduce free electrons as the majority charge carriers because they have an extra valence electron compared to silicon's four valence electrons.
3. Aluminum and Boron are trivalent elements, which create P-type semiconductors by introducing holes as the majority charge carriers.
4. Germanium is another semiconductor material, not typically used as a dopant for silicon.