Correct option is B
(A) It can be understood as a line of reasoning that intends to show or explain why a mathematical result is true.
(B) A mathematical argument might be a formal or informal proof.
(C) It can also be a part of the Heuristic approach in mathematics education.
(D) "It cannot be used for teaching mathematics as argumentation is important only for social science" is not true. Argumentation is a critical component of mathematical thinking and education, not just social science.