Final answer:
The best description for customers who frequently pay bills late, make excuses, and blame others is 'immature'. Option (d) Immature fits this behavior which indicates a lack of responsibility and accountability.
Step-by-step explanation:
Customers who frequently pay bills late or not at all, who make excuses for their actions, and blame others for their problems are typically considered immature. This behavior often reflects a lack of responsibility and an inability to take accountability for one's actions.
Option (d) Immature is the best fit for these characteristics, as the other options do not adequately describe the behaviors mentioned in the question.