[求助]新人求解 大全A-7

有谁能帮忙解释一下思维过程吗?

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.

答案说是C  可是那跟B和E的区别在哪里呢?

谢谢

always remember this: if A ---> B, then Not B ----> not A

Now in the statement above, since A ---> D, So Not D ----> Not A

Hence, C is the answer