Himpunan semua nilai x agar fungsi y = (x^2 -1)/(x^2 + 1)

Himpunan semua nilai x agar fungsi y = (x^2 -1)/(x^2 + 1) terdefinisi adalah... A. {x | 0 < x < 1, x e R} B. {x | -1 < x < 1, x e R} C. {x | -1 < x <= 1, x e R} D. {x |x e R} E. {x | x e R, x =/= 2,x =/= -1}