Which of the following elements do international agreements set terms and conditions for?

International agreements serve as formal arrangements between countries that define the terms and conditions for a variety of cooperative activities. Choosing "all of the above" indicates an understanding that these agreements encompass various areas of collaboration, including joint research and development, personnel exchanges, and military sales.

Joint research and development initiatives often require clear stipulations regarding intellectual property rights, funding responsibilities, and distribution of benefits, all of which would be governed by international agreements. Personnel exchanges necessitate guidelines related to security clearance, training responsibilities, and the duration of exchanges to ensure proper management of personnel across borders. Likewise, military sales agreements are crucial for establishing the legal framework under which defense articles, services, and technology can be transferred between nations, often including considerations around pricing, delivery schedules, and compliance with export controls.

Thus, the correct answer reflects the comprehensive nature of international agreements in governing a wide range of activities that involve collaboration between nations.