It is a kind of cooperation in which the countries share ideas and information with their rivals. What is been talked about?

Confidence Building

The correct answer is Option 3 - Confidence Building

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.