A: external unstable; internal stable

    Incorrect.
External unstable causes of failure in school would be things such as: bad luck and bad teachers, while examples of internal stable cause of failure in school are: lack of ability and  lack of discipline.  While it might be okay to retrain students to cease attributing their academic to bad luck and bad teachers (external unstable), it would not be good to have students attribute their behavior to lack of ability and lack of discipline (internal stable).  If people changed their attribution of failure to their lack of ability, they would feel helpless to improve.