Hey there!
In order to simplify this, we'll first have to use the distributive property, which is defined as:
a(b+c) = ab + ac
Therefore, we would distribute that -4, remember that it is a negative and to follow those rules to get:
8-12+8m+2m =
-4 + 10m =
10m - 4
Your answer is A.
Hope this helps!