A. True
(m - n) (m - n) = m(m - n) - n(m - n)
Expanding the expression, we get:
(m - n) (m - n) = m^2 - mn - mn + n^2
Simplifying the middle terms, we get:
(m - n) (m - n) = m^2 - 2mn + n^2
We can see that the middle terms, -2mn, have a sum of zero since they are opposites, or a zero pair. Therefore, the statement "the middle terms have a sum of zero" is true