The correct answer is 33%.

• 33% of members of Rajya Sabha retire every two years.

• The Vice-President is the Ex-officio Chairman of the Rajya Sabha.
• Rajya Sabha was constituted on 3rd April 1952.
• Rajya Sabha is constituted under Article 80.
• The fourth schedule to the constitution deals with the allocation of seats in the Rajya Sabha to the States and Union Territories.
• It is known as the 'Upper House'.
• It is known as the 'Council of States'.
• It is a permanent body and is not subject to dissolution.
• The maximum strength of the Rajya Sabha is fixed at 250 (238 are elected members and 12 members are nominated by the President) having special knowledge or practical experience in the fields of science, literature, arts, and social service.
• At present, there are 245 members in the Rajya Sabha. Out of which 233 are elected members and 12 are nominated members.
• There is no seat reserved for SCs and STs in Rajya Sabha.
• The tenure of a member of the Rajya Sabha is 6 years.
• One-third of its members retire every two years.
• The members are indirectly elected and nominated by means of a single transferable vote.