try taking it one step at a time and multiplying each set one by one. watch the negative signs! remember: a negative times a positive is negative, and a negative times a negative is positive!
-2m(m+n-4)= -2m^2 -2mn+8m
next:
5(-2m+2n) = -10m+10n
next:
n(m+4n-5) = nm + 4n^2-5n
you're left with
-2m^2-2mn+8m-10m+10n+nm+4n^2-5n
now, add "like terms" (aka terms that have the same letters and powers, like 10n and -5n)
So,
-2m^2-nm-2m+5n+4n^2
is your answer! (answer choice C.)