Step 1: Understand different types of communication.
Communication can be classified based on the number of participants and the nature of interaction.
Step 2: Analyze the classroom communication scenario.
In a typical classroom setting, a teacher communicates with a group of students. While there might be elements of face-to-face and interpersonal interactions, the overarching communication type is with the entire class or smaller subgroups within it.
Step 3: Evaluate the given options in the context of a classroom.
(1) Face to face communication: While communication in a classroom is often face-to-face, this term describes the \textit{mode} of communication (physical presence) rather than the \textit{type} in terms of the number of participants. A one-on-one conversation is also face-to-face.
(2) Group communication: This refers to communication that takes place within a group of people, where individuals interact and share information with each other. A classroom, consisting of a teacher and multiple students, functions as a group, making 'group communication' the most appropriate term for the overall communication dynamic.
(3) Mass communication: This involves transmitting a message to a very large, diverse, and often anonymous audience through mass media (e.g., television, radio, newspapers). This is not applicable to a typical classroom.
(4) Inter-personal communication: This typically refers to communication between two individuals. While a teacher might have individual interactions with students, the general communication in a classroom setting, involving multiple students, is broader than just interpersonal.
Step 4: Conclude the correct option.
The primary mode of communication by a teacher in a classroom, addressing multiple students simultaneously, falls under the category of group communication.