You are conversing with a colleague over a secure instant message system. This conversation contains classified information in the body of the conversation. You need to save the conversation for later use. What markings will apply

All standard class. markings

Explanation:

All standard class markings are the most suitable necessary to save for future reference when conversing with a colleague over a secure instant message system.

This conversation contains classified information in the body of the message or conversation which we can go back to have them intact.