\item \self Look at the following statements and tick them if they are true. \begin{itemize} \item[$\square$] You need an assumption box, if you want to eliminate an implication. \item[$\square$] You need an assumption box, if you want to introduce a negation. \item[$\square$] You need an assumption box, if you want to use the Modus Tollens. \item[$\square$] You need an assumption box, if you want to use the Law of the Excluded Middle \end{itemize}