Conformity to the demands of the situation is central to the fuller treatment of rhetorical appropriateness. A sentence must not only be linguistically sound; its form must suit the audience, purpose, and circumstances.
Situation 1: someone merely asks the time; a clear short answer may be ideal.
Situation 2: the same person asks for the reasoning behind a difficult decision; an equally short reply may be inadequate.
The words in either reply may be correct. What changes is the kind of expression the context requires. This is a property assessed at the level of discourse.