Answer:
B. She was happy because the arm helped Christopher to do something on his own.
Step-by-step explanation:
Without the mechanical arm, Christopher Rhoades could not do simple activities, such as taking objects out of his own backpack. This limited his autonomy and made him very dependent on people's help. Of course, it made Christopher sad and often ashamed, which made Cristopher's mother equally sad because she wanted her son to live to the full. However, the mechanical arm gave Christopher the autonomy he needed, which not only increased his freedom, but also increased his self-esteem. This made his mother very happy.