Explanation:

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 Given that The victim has been murdered by a knife during a stormy night at her residence in a small town. 
 It is known that for each of them, one statement is correct and one statement is wrong, 
A:  I.  I have never touched a knife in my life.  
 II.  I was not in town on the night of the murder. 
According to Both the statements A is not the murderer. But cann't conclude which statement is true
B:   I.  A is the murderer.  (wrong)
 II.  I was playing cards with C the entire night of the murder. (correct)

C:  I.  I was sleeping on the night of the murder.   ( Wrong)
II.  B is innocent.  (Correct)

Here we can easily conclude that A,B,C are innocent. means D is he murderer

D:  I.  C is innocent.   (correct)
II.  B is the murderer.(wrong)

Here we  can conclude 4th option ( I was sleeping on the night of the murder.)   ( Wrong)