Given the following function:

We will find the domain of the function f(x)
As shown, it is a rational function and there is a square root in the denominator
So, the domain is all real numbers except the values that make the denominator zero or negative
So, we need to solve the following inequality:

We will solve the inequality as follows:

So, the answer will be
D. all real numbers such that x > 2, x < -2