what does the definition of "partial order" say?

you have to show that reflexivity, antisymmetry and transitivity holds

see: Partial Order -- from Wolfram MathWorld

see here(b) draw the Hasse diagram for<

again, what you need to do here becomes clear when you write out the definitions, which i won't do since that's reinventing the wheel. check your text, or google, or wikipedia, or ....(c) List all minimum, minimal, maximum, and maximal elements.

in addition to being a partial order, can any two elements be compared?(d) Is (A, <) totally ordered? explain

see: Totally Ordered Set -- from Wolfram MathWorld