A:白:粉:红,3:10:3
B:白:粉:红,3:12:1
C:白:粉:红,4:9:3
D:白:粉:红,6:9:1
They promised to develop a software package by the end of this year, ____ difficulty they might have.
若单项式-2x2y3的系数是m,次数是n,则mn的值为 ( )