Determine whether the relation R on the set of all real numbers is reflexive, symmetric, antisymmetric, and/or transitive, where (x, y) ∈ R if and only if
a) x + y = 0.
b) x = ± y.
c) x - y is a rational number.
d) x = 2y.
e) xy ≥ 0.
f) xy = 0.
g) x = 1.
h) x = 1 or y = 1.