Leibniz was a great philosopher of the 17th century. He published his results of calculus research before Newton. But at that time Newton published his personal notes, stating that he had applied the principle of calculus at least 10 years before Leibniz published his results. Newton also said that not long before Leibniz published his results, he talked about his thoughts on calculus in a letter to Leibniz. But the post-hoc research showed that in this letter from Newton, the few lines of calculus did not touch on any significance of this theory. Therefore, it can be concluded that Leibniz and Newton each independently invented calculus. Which of the following must be assumed in the above argument. ['Leibniz has no less talent in mathematics than Newton.', 'Leibniz and Newton are honest people.', 'No third person independently invented calculus no later than Leibniz and Newton.', 'Neither Leibniz nor Newton gets key details about calculus from a third channel.']