6. Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen:
(A) the stress encountered when the stress-strain curve transforms from elastic to plastic behavior,
(B) the maximum load divided by the final area of the specimen,
(C) the maximum load divided by the original area of the specimen,
(D) the stress observed when the specimen finally fails
(E) none of the above?