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If A, then B.

If B, then C.

If C, then D.

If all of the statements above are true, which of the following must also be true?

(A) If D, then A.

(B) If not B, then not C.

(C) If not D, then not A.

(D) If D, then E.

(E) If not A, then not D.

c是正确的

因为

If A, then B.

If B, then C.

If C, then D.

可以推出if a,then D.

那么，逆否一下就是答案c