Answer: First option.
Step-by-step explanation:
Given two sets <em>A</em> and <em>B, </em>the union (<em>A</em>∪B) will be the set of elements which belong to either <em>A</em> or to <em>B</em> or to both.
Inf this case you have these two sets:
{} and {}
To find the union of these sets, put together the elements of the set <em>P</em> and the elements of the set <em>Q</em> (you need to remember that no element must be repeated).
Then, you get that the union of sets <em>P </em>and <em>Q</em> is:
∪{}
This matches with the first option.