Administering pre-operative antibiotics is essential to prevent post-operative infection in a patient undergoing amputation. Prophylactic antibiotics are often given before the surgical procedure to reduce the risk of infection at the surgical site and promote successful wound healing.
  
b. Providing pre-operative analgesia: Providing pre-operative analgesia is important for pain management, but it is not directly related to preventing post-operative infection.
c. Ensuring proper patient positioning: Ensuring proper patient positioning is crucial for the surgical procedure's success and patient safety, but it is not directly related to preventing post-operative infection.
d. Educating the patient about post-operative exercises: Patient education about post-operative exercises is important for rehabilitation, but it does not directly prevent post-operative infection. Proper wound care and infection prevention protocols are more relevant to reducing the risk of infection.