Exp) Option b is the correct answer.

• A democratic polity, as stipulated in the Preamble, is based on the doctrine of popular sovereignty, that is, possession of supreme power by the people.
• Democracy is of two types–direct and indirect. In direct democracy, the people exercise their supreme power directly as is the case in Switzerland. In indirect democracy, the representatives elected by the people exercise supreme power and thus carry on the government and make the laws. This type of democracy, also known as representative democracy.
• The Indian Constitution provides for representative parliamentary democracy under which the executive is responsible to the legislature for all its policies and actions.