ANSWER
D.
[tex] {x}^{6} - x + \sqrt{6} [/tex]
EXPLANATION
A trinomial is a simplified polynomial with three terms.
The first option is not a polynomial because of the presence of √x.
The second option is not a trinomial because it has only two terms.
The third option is not a polynomial because of the presence of
[tex] \frac{1}{x} [/tex]
The last option:
[tex] {x}^{6} - x + \sqrt{6} [/tex]
This is trinomial because it has three terms and cannot be simplified further.
There is not fractional exponent.
