The *cardinality* of a set $S$ is the *number of elements in $S$*.

Common notations for the cardinality of a set $S$ are ${\rm Card}(S)$, and $|S|$.

We use $|S|$.

An infinite set $S$ has cardinality $|S|=\infty$.

The empty set $S=\emptyset$ is the set with no elements and $|\emptyset|=0$.

Which of the following $S$ sets has $|S|=7$? (Select all that apply.)