Manipulate the equation like this:
j + k = 2j + 4
j + k – 2j = 4
k – j = 4
It is not important whether j and k are even individually because
an odd number minus an odd number = an even number. An even number
minus an even number = an even number. As long as they are the same,
then an even number results. So the only thing that is necessarily
true is that k – j is even.
(D)