Which of the following is the expansion of (2m - n)^7?
a)128m^7+448m^6n+672m^5n^2+560m^4n^ 3+280m^3n^4+84m^2n^5+14mn^6+n^7
b) 128m^7+14m^6n+42m^5n^2+70m^4n^3+70m ^3n^4+42m^2n^5+14mn^6+n^7
c) m^7+7m^6n+21m^5n^2+35m^4n^3+35m^3n^ 4+21m^2n^5+7mn^6+n^7
d) 128m^7-384m^6n+480m^5n^2-320m^4n^3+ 160m^3n^4-60m^2n^5+12mn^6-n^7
e) 128m^7-448m^6n+672m^5n^2-560m^4n^3+ 280m^3n^4-84m^2n^5+14mn^6-n^7