Hi, I am stuck on this question too. I guess you are also an ILC student!!
I think this diagram would have 4 circles, except that they will not intersect, which is where I am confused. Unless d =S, which is the universal set... Or a, b, and c are all smaller circles within the big circle D...
and D would be all of it, so -4,-3,-2,-1,0,1,2,3,4
I went onto Tutor.com, but the tutor could not figure it out... but this seems to make the most sense to me.
Check out my attatchment
What do you think?