Answer:
D. overconfidence phenomenon.
Explanation:
According to my research on studies conducted by various psychologists, I can say that based on the information provided within the question your brother's behavior can be explained by the overconfidence phenomenon. The phenomenon is a behavioral bias in which a person's confidence in his or her position/statements is reliably greater than the objective accuracy of those statements.
I hope this answered your question. If you have any more questions feel free to ask away at Brainly.