The right answer is self-serving.
The concept of self-serving bias refers to the tendency of people to attribute the causality of their success to their own qualities (internal causes) and their failures to factors that do not depend on them (external causes), in order to maintain positive their self-image.
For example, an individual will justify getting a good mark on an exam by referring to the work they have done while explaining that they get a bad mark by the severity of the proofreader.