Answer
$\overline{AD}$
Work Step by Step
The union of $\overline{AC}$ and $overline{BD}$ is the set of points which is in either of those sets:
$\overline{AD}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.