a) a+d=b+c this statement is obvious as if a=n,b =n+2,c=n+4 and d=n+6 then a+d=b+c
b) b+c=a-d
if a =n then d=a+6(as a,b,c,d are consecutive even integers)
b+c=6=a+d
hence B
b) b+c=a-d
if a =n then d=a+6(as a,b,c,d are consecutive even integers)
b+c=6=a+d
hence B
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