If $U$ is the set of all integers and $A$ is the set of all negative integers, then $A'$ = ?

Question

Accepted Answer

$\{0, 1, 2, 3, \ldots\}$

Answer

$\{\ldots, -3, -2, -1\}$

Answer

$\emptyset$

Answer

$\{0\}$

If UUU is the set of all integers and AAA is the set of all negative integers, then A′A'A′ = ?