Answer:
C. It emphasizes how the narrator felt about his brother.
Step-by-step explanation:
The language and style always contribute to express the intensity of the emotion or actions displayed in the text. In this passage also, the word "extreamly" emphasizes and enhances the depth and height of the author's misconception about his brother. It echoes the utter delusion of the author for his brother as he sent him for the apprenticeship and elaborates on his immature actions led by it. Thus, we may conclude that the word "extreamly" employed to emphasize the narrator's mixed-up feelings for his brother that was a great "amiss" which he realizes later.