Working of institution

Why is the Prime Minister in India not directly elected by the people? Choose the most appropriate answer and give reasons for your choice.
a In a Parliamentary democracy only the leader of the majority party in the Lok Sabha can become the Prime Minister.
b Lok Sabha can remove the Prime Minister and the Council of Ministers even before the expiry of their term.
c Since the Prime Minister is appointed by the President there is noneed for it.
d Direct election of the Prime Minister will involve lot of expenditure on election.