1951 AHSME Problem 14

In connection with proof in geometry, indicate which one of the following statements is *incorrect*:

\textbf{(A)}\ \text{Some statements are accepted without being proved.} \textbf{(B)}\ \text{In some cases there is more than one correct order in proving certain propositions.} \textbf{(C)}\ \text{Every term used in a proof must have been defined previously.} \textbf{(D)}\ \text{It is not possible to arrive by correct reasoning at a true conclusion if, in the given, there is an untrue proposition.} \textbf{(E)}\ \text{Indirect proof can be used whenever there are two or more contrary propositions.}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.