Answer: Choice D) set of even integers
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Explanation:
U = universal set = {all positive integers} = {1, 2, 3, 4, 5, ...}
A = {stuff in set U that is odd} = {1, 3, 5, 7, 9, ...}
[tex]A^c[/tex] = {stuff in set U but NOT from set A} = {2, 4, 6, 8, ...}
[tex]A^c[/tex] = {set of even numbers from set U}
In set theory, the complement is simply the complete opposite. If the number 7 is found in set A for instance, then 7 is not going to live in the complement [tex]A^c[/tex]
The opposite of the odd numbers is the set of even numbers.
Therefore, we go for choice D as our final answer.
Side note: if we union set A with its complement [tex]A^c[/tex] then we get the universal set as a result. [tex]A \cup A^c = \text{universal set} = \text{set of all positive integers}[/tex]