Concept:A conjecture in mathematics is an unproven statement that appears true based on patterns or observations.Explanation:Mathematicians often notice patterns and form a conjecture as a tentative conclusion.It lacks formal proof and is not considered a theorem yet.Conjectures guide further exploration and investigation.Thus, a conjecture is a proposition assumed true on a tentative basis without proof.Answer:D. a proposition or conclusion that is assumed to be true on a tentative basis without proof.