Which set of functions f satisfying the given condition IS NOT a subspace of the vectorial space F(|R) of real functions with real variable. a) f(x) = -f(x), for every x ∈ |R
b) f(0) = 0
c) f(x) = k, for every x ∈ |R, with k as a non zero real constant.
d) f(-x) = f(-x), with x ∈ |R