The correct answer is D) The same utterance should have the same meaning in a different context.
The option that is NOT a fundamental assumption of conversation analysis is "The same utterance should have the same meaning in a different context."
We are talking about the study of the type of conversations people have when they are interacting on a daily basis. It could be in the family environment, in school, in the workplace, or in any activity. That is a conversation analysis. It is part of sociolinguistics, and Harvey Sacks is one of the first sociologists to refer to this topic.