The correct answer is: C. horizontal communication.
Horizontal communication is communication that takes place between people at the same level in an organization. It can be used to share information, coordinate work, and build relationships.
Downward communication is communication that takes place from a higher level to a lower level in an organization. It is often used to give instructions, provide feedback, and set goals.
Upward communication is communication that takes place from a lower level to a higher level in an organization. It is often used to share information, provide feedback, and suggest improvements.
Informal communication is communication that takes place outside of formal channels, such as email or meetings. It can be used to share information, build relationships, and resolve problems.
In the case of an inter-departmental committee meeting, the participants are all at the same level in the organization. They are meeting to share information, coordinate work, and build relationships. Therefore, the meeting is an example of horizontal communication.