Answer:
For WXYZ to be a parallelogram, both pairs of opposite sides must be parallel.
So, we have 7m + 4 = 9m and 5y + 13 - (2n - 1) = 6y - 8 - (n + 6).
Solving the first equation, we get m = 2.
Solving the second equation, we get y - n = 4.
Thus, for WXYZ to be a parallelogram, m = 2 and y - n = 4, so option B is correct.