Answer: Two separated circles, one called X and the other called Y.
(so there is no element of the set X that is also in the set Y)
Explanation:
"No X are Y"
This means that there is not a single element in the set X that is also in the set Y.
So in an Euler diagram, you can represent this as two circles, one called Y and other called X, where the circles do not intersect or touch at any point.
This particular case is represented similarly to how you would represent it in a Venn diagram