The correct answer is (c) Judiciary.
The Judiciary is the guardian of the fundamental rights in India. The Supreme Court and the High Courts have the power to strike down any law that they find to be unconstitutional. They also have the power to issue writs to protect the fundamental rights of citizens.
The Parliament is the legislative body of India. It has the power to make laws, but it cannot make laws that violate the fundamental rights. The President is the head of state of India. He has the power to sign laws into effect, but he cannot sign a law that violates the fundamental rights. The Prime Minister is the head of government of India. He has the power to advise the President on matters of policy, but he cannot advise the President to sign a law that violates the fundamental rights.
The Judiciary is the only institution that is independent of the other two branches of government. It is therefore the only institution that can effectively protect the fundamental rights of citizens.