X is a subset of Y and Y is a subset of Z. Which of the following statements must be true?
(A) If 1 is in Y, then 1 is in X.
(B) If 2 is in Z, then 2 is in X.
(C) If 3 is in Z, then 3 is in Y.
(D) If 4 is in X, then 4 is in Z.
(E) None of the above