Answer:
D. I and III only
Explanation:
I is true - look at either chains and take the first and last element.
III is also true, looking at the last part of the second chain of inequalities.
II can be false, since the only thing we know about x and y is that both are somewhere inbetween w and z. Either of the two points in the line can be x or y, and we have no idea which one is the leftmost one. Thus solution is D