A process of exchanging information in defence matters between nation on regular basis came under :

Confidence Building Measures

The correct answer is option (3) - Confidence Building Measures

Confidence building is a process in which countries share ideas and information with their rivals. They tell each other about their military intentions and, up to a point, their military plans. This is a way of demonstrating that they are not planning a surprise attack. They also tell each other about the kind of forces they possess, and they may share information on where those forces are deployed. In short, confidence building is a process designed to ensure that rivals do not go to war through misunderstanding or misperception.