Explanation: The statement is incorrect. According to the Supreme Court's ruling, each High Court may appoint 2 to 5 ad-hoc judges, not exceeding 10% of its sanctioned strength, not 15% as stated in the option. The other statements are correct: ad-hoc appointments can be made even if vacancies don't exceed 20% of sanctioned strength, ad-hoc judges will hear criminal appeals in benches headed by sitting judges, and Chief Justices can recommend retired judges for ad-hoc appointments.
Explanation: The statement is incorrect. According to the Supreme Court's ruling, each High Court may appoint 2 to 5 ad-hoc judges, not exceeding 10% of its sanctioned strength, not 15% as stated in the option. The other statements are correct: ad-hoc appointments can be made even if vacancies don't exceed 20% of sanctioned strength, ad-hoc judges will hear criminal appeals in benches headed by sitting judges, and Chief Justices can recommend retired judges for ad-hoc appointments.