To enforce the Fundamental Rights the Court issues :

The correct answer is (a) writ.

A writ is a court order that compels a person to do something or to refrain from doing something. Writs are issued by the courts to enforce the Fundamental Rights of citizens.

A decree is a court order that settles a dispute between two parties. Decrees are issued by the courts after a trial.

An ordinance is a law that is passed by a local government.

Therefore, the correct answer is (a) writ.