Answer: All the real values except x ≠ 7 and the x for which f(x)≠-3
Step-by-step explanation:
Since, For function f , the domain is R - {7}
That is, If x is any element of the domain of the function f,
Then,  x ≠ 7 
(gof)(x) = g(f(x)) 
Since, For the function g, the domain is R - {-3}
Thus,  If f(x) is any element of the domain of the function g,
Then f(x)≠ -3
Hence, Fourth Option is correct.