The correct answer is: B. informal communication.
A grapevine is an informal communication network that typically arises in an organization when the formal communication channels are not working effectively. It is often used to share information that is not officially sanctioned, such as rumors or gossip.
Formal communication is a system of communication that is established and regulated by an organization. It typically includes channels such as email, memos, and meetings. Formal communication is often used to share information that is official or that needs to be communicated to a large number of people.
Informal communication is a system of communication that is not established or regulated by an organization. It typically includes channels such as water cooler talk, hallway conversations, and social media. Informal communication is often used to share information that is not official or that needs to be communicated to a small number of people.
In conclusion, the term “grapevine” is used in relation to informal communication.