Let $X, E_1, \ldots, E_N$ each be a D11: Set such that

(i) | $\bigcup_{n = 1}^N E_n$ is the D77: Set union of $E_1, \ldots, E_N$ |

Then
\begin{equation}
\bigcup_{n = 1}^N E_n
\subseteq X
\quad \iff \quad E_1 \subseteq X, \; \ldots, \; E_N \subseteq X
\end{equation}