which of the following is a polynomial?

A.
[tex] \frac{1}{x} + 2[/tex]
B. x
[tex] { x}^{2} - 1[/tex]
C.
[tex] \frac{(x {}^{6} - 2)}{(x { }^{ - 4} + 3)} [/tex]
D.
[tex] {x}^{4} + {x}^{ - 4} + 16[/tex]