Formal communication refers to the transmission and exchange of information in an organizational system based on certain organizational principles, such as official correspondence between organizations, communication of documents within the organization, holding meetings, and regular information exchange between superiors, In addition, visits, technical exchanges, and market surveys organized by groups are also included. What are the formal communication channels below? ['Gossip.', 'Friends gathering.', 'Lunch in the cafeteria.', 'Staff meetings.']