For a suitably chosen real constant `a,` let a function, `f(x) : R – {a} rarr R` be defined by `f(x) =(a-x)/(a+x).` Further suppose that for any real number `x ne –a` and `f(x) ne –a,` `(fof)(x) = x.` Then `f(-1/2)` is equal to

Options

A. `1/3`
B. `3`
C. `-3`
D. `-1/3`