a) Yes, of course. Z+ X Z+ covers all pairs (a,b), where a,b are in Z+
b) Yes. any number in Z+ divides itself
c) Yes. If a,b are in Z+ , a divides b AND b divides a => a = b
d) Yes. R is total because there is b in Z+ for every a in Z+. Namely, a. That is, in plain English, for every positive integer, there exists a positive integer which can be divided by it.
e) Yes. R is a partial order if it is reflexive, antisymmetric, and transitive. R is transitive because if a divides b, and b divides c, a divides c. Again, a,b,c are in Z+