The domain of a function f(x) is the set of all values for which the function is defined, and the range of the function is the set of all values that f takes.
A constant function is a linear function whose range contains only one element irrespective of the number of elements of the domain.
Since a constant function is defined for all real values of x, then we have that:
1) Its domain is the set of all real numbers, and
2) Since a constant function f(x) = c leads to only one output, which is k, its range is the set with just one element c.
Therefore,

The statement is TRUE.