Q13

Every subset of a recursively enumerable language is recursive.

If a language $\textit{L}$ and its complement $\overline{\textit{L}}$ are both recursively enumerable, then $\textit{L}$ must be recursive.

Complement of a context-free language must be recursive.

If $\textit{L}_{1}$ and $\textit{L}_{2}$ are regular, then $\textit{L}_{1} \cap \textit{L}_{2}$ must be deterministic context-free.