Detailed Solution:
The correct answer is “Not exceeding one year”.
Article 249 of the Constitution provides that if the Rajya Sabha feels that it is necessary in the national interest that Parliament should make laws on any matter in the State List, it may pass a resolution to that effect by a two-thirds majority of the members present and voting.
Once such a resolution is passed, Parliament is empowered to make laws on the specified matter for a period not exceeding one year.