1
The question:
Let $L_1,L_2,...$ be an enumeration of $\mathcal{R}$ and define $A_i = \{\langle M\rangle \ | \ L(M) = L_i\}$. Let $L$ be a language in $\mathcal{RE}$ such that $L \subset \{\langle M\rangle \ | \ \text{M is a TM that always halts}\}$. Prove that
there exists an $i$ for which ...