Answer: Choice D. 2 ≤ x ≤ 9
Reason:
The domain is the set of allowed x inputs.
We look at the x coordinates of the endpoints.
The left-most point is when x = 2.
The right-most point is when x = 9.
The set of x values span between 2 and 9, including each endpoint. So we would say 2 ≤ x ≤ 9