The ans is C but i don't know why?
I think B or D stand a better chance.
Cld u pls explain
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.
Take an anlogy -
All dogs are animals ( X then Y)
IF Not animal then NOT dog --- this will be true (Not Y then Not X is true)
But if we say if Not Dog then Not Animal (Not X then Not Y) - Can this be True?
The answer is both Yes and No - A Cat is Not a Dog but still a Cat is an Animal. Hence FALSE.
A Machine is not a Dog and is Not an Animal either. Hence TRUE
Hence Not X then Not Y cannot be determined with certainty.
Remember if X gives Y
then it follows logically that - Not Y IS Not X
But Not X does not necessarily mean Not Y.