Find the infimum and supremum, if they exist, of each of the following sets.
(a) A: = {x ∈ R : 2x + 5 > 0};
(b) B: = {x ∈ R : x + 2 > x2}
(c) C: = {x ∈ R : x < 1/x};
(d) D: = {x ∈ R : x2 - 2x - 5 < 0}