Homogeneity of opinion among groups of people is mostly caused by

The correct option is Inter-personal communication.

Homogeneity of opinion, or the tendency of individuals within a group to share similar views, beliefs, and attitudes, is primarily driven by direct, face-to-face interactions among individuals.
When people engage in inter-personal communication, they exchange ideas, negotiate meanings, and build mutual understanding on a personal level. Over time, this continuous dialogue, feedback, and social influence lead to the alignment of opinions and the formation of a consensus within the group.

Let's look at why other forms of communication are less responsible for group homogeneity:
1. Mass communication: While it reaches a large audience, it is a one-way process and often leads to diverse interpretations rather than a unified group opinion.
2. Intra-personal communication: This is communication with oneself (thinking, self-reflection) and does not involve the social interaction necessary to align opinions with others.
3. Abstraction in communication: Using abstract terms can actually lead to ambiguity and different interpretations, rather than homogeneity of opinion.

Therefore, personal dialogue and direct social influence inherent in inter-personal communication are the primary drivers of shared group opinions.