Question

E.
Suppose that G = (PUR, E) is acyclic. If we identify a minimal elementre
R of G that is isolated (i.e. there are no edges in or out of r) then this still
does not allow us to progress. Argue that if all r ER are isolated, then
there must also exist a minimal element p EP. Note that any isolated
vertex is a minimal element.​

Answer 1

I did some research on the question you had asked. Unfortunately I have seen this question comeback from a test question which isnt allowed here.

Reported,

Have a nice day