$\varnothing$: Setting Things Straight

$\varnothing$: Setting Things Straight



Question: Let $S=\{\varnothing, \{\varnothing\}\}$. Which of the following
are/is true?
$\varnothing\subseteq S$
$\varnothing\in S$
$\{\varnothing\}\subseteq S$
$\{\varnothing\}\in S$



OP's Answer: All are true.