Calculus question If functions f and g have domains Df and Dg respectively

If functions f and g have domains Df and Dg respectively, then the domain of f / g is given by

(A) the union of Df and Dg
(B) the intersection of Df and Dg
(C) the intersection of Df and Dg without the zeros of function g
(D) None of the above

Let the closed interval [a , b] be the domain of function f. The domain of f(x – 3) is given by

(A) the open interval (a , b)
(B) the closed interval [a , b]
(C) the closed interval [a – 3 , b – 3]
(D) the closed interval [a + 3 , b + 3]