Joint Military exercise 'Keen Sword 23' was conducted between :

Keen Sword 23 is a biennial joint field training exercise (FTX) conducted between the United States military and the Japan Self-Defense Forces (JSDF). It is one of the largest military exercises in the Indo-Pacific region.

• Purpose: The exercise is designed to enhance the interoperability and combat readiness of the U.S.-Japan alliance, ensuring both nations can respond effectively to regional crises or contingencies.
• Scope: The 2023 edition (conducted in November 2022) involved comprehensive training in amphibious operations, integrated air and missile defense, and maritime security.
• Location: It took place at various locations across Japan, including the Nansei Islands, reflecting the strategic focus on regional stability.
• Participants: While primarily a bilateral exercise between the USA and Japan, other partner nations like Australia and Canada often participate as observers or with limited assets to promote a 'Free and Open Indo-Pacific'.

Therefore, Option C is correct.