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\begin{questionEnumerate}[0.2em]
\item Explain what it means that natural deduction for propositional logic is \emph{complete}?
\item Sketch the idea of the \emph{proof for completeness} of natural deduction for propositional logic. List the three sub-proofs that need to be performed to prove completeness and briefly discuss the idea of each individual sub-proof.
\end{questionEnumerate}