Intrinsic semi-conductor can be converted into extrinsic semi-conductor by adding:

Explanation

Intrinsic semiconductors, like silicon (Si) and germanium (Ge), have equal numbers of electrons and holes. By adding a small amount of impurity, known as doping, the semiconductor's electrical properties can be modified, turning it into an extrinsic semiconductor. Trivalent impurities, such as boron (B), create a p-type semiconductor by introducing holes, while pentavalent impurities, such as phosphorus (P), create an n-type semiconductor by providing additional electrons. Therefore, both types of impurities can convert intrinsic semiconductors to extrinsic ones, which is why Option C is correct. Option A and Option B are partially correct but do not encompass the full solution, and Option D is incorrect as both impurity types are valid.