Hello Shia... I lean toward B on this one. If I could only choose from those, I'd pick B. The truth is that this statement in English can have MANY different meanings. Almost as many meanings as there are for actually making excuses in the first place haha.
You might say 'I'm not going to make excuses FOR YOU anymore', meaning that you won't continue to defend someone who doesn't deserve defending. You could say 'I'm not going to make excuses' as in 'I don't owe you an explanation for my own choices'. Or you could mean that 'I'm accepting responsibility for my actions, and therefore I'm not going to make excuses anymore'. Regarding option 'A', in English, an 'excuse' may be truthful OR it may not. A truthful valid excuse, or a fabricated lie excuse, actually are both 'excuses' lol.
So it could mean a lot of different things :) Hope this helps!