Observation

This question was not popular among the candidates.  Few that attempted it performed poorly.
Part (a).  Performance was poor.
Part (b).  Diagram was not properly drawn.  Majority were drawing the symbol for AND gate.
The expected answers are:
(5. (a)     Doping is the addition of  impurity (atoms) to a  (pure)
semiconductor  to increase its ( electrical ) conductivity  through increase in the
number of holes and electrons / charge carriers.

OR Gate