question_answer

Directions : In the following question more than one of the answers given may be correct. Select the correct answer and mark it according to the code:

The impurity atoms with pure silicon should be doped to make a n-type semiconductor are those (1) phosphorus                 (2) antimany (3) boron                             (4) aluminium

A)   1, 2 and 3 are correct

B)  1 and 2 are correct

C)   2 and 4 are correct

D)  1 and 3 are correct