Domain:
The domain of a function f(x) are all possible values that x can assume.
Sometimes, such in fractions or in square roots, x has constraints. In other cases, x has no constrains, so the domain is all real numbers.
In this exercise:
F(x) = 5
This means that for each value of x, y = 5.
In the function, there are no fractions or roots, so the domain is all real numbers.
The correct answer is:
B. all real numbers
