I need help finding the domain.

2 The function f(x) = - 7 + x is one-to-one. (a) Find its inverse and check your answer. (b) Find the domain and the range of f and f. (a) f ( x ) = --7 (Simplify your answer.) X (b) Find the domain of f. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The domain is {xxs (Type integers or fractions. Use a comma to separate answers as needed.) O B. The domain is {x|x # (Type integers or fractions. Use a comma to separate answers as needed.) O C. The domain is {xx 2 (Type integers or fractions. Use a comma to separate answers as needed.) O D. The domain is the set of all real numbers