Easy one for a change, so give yourself 10 seconds to work it. It’s a single water hose with the ends uncoupled. Where are the ends?
Post your answer in the comment section below.
Update and solution
The solution is straight-forward. See the revised picture below.
Draw circles (ellipses) around A and B. Each has three hoses crossing into (or out of) the ellipse. Therefore, there must be a hose end within each of the two ellipses. Since there are only two ends (one hose), the ends must be under A and B. You don’t need to examine C and D, but if you do you will observe an even number of crossings.