Which of the following represents a chord, but not a diameter, of the circle?

you don't have an image or a diagram, so I'll just show you what a chord is.

Think of the circle as a small pizza, and your sharing it with a sibling. You would want your sibling to split it in half equaly, right? The diameter splits the pie perfectly in half going straight through the center of the pie. Now, if your sibling was being plain mean, they'd make it so in was uneven and they'd give themselves the bigger half and would give you the tiny piece. That's like a chord, it doesn't go through the center. Remember that a chord stops at the edge (idk what to call it) of the circle, it doesn't continue on (if it did continue on, that would be called a secant).

I hope that clarifies things for you!

(p.s. I attached an image for you to look at :) )  

yes.. it's proven to be 36.