Final answer:
The internationally defined temperature indicative of a postpartal infection on the third day postpartum is 100.4°F (38°C).
Step-by-step explanation:
On the third day postpartum, the temperature internationally defined as a postpartal infection is B. 100.4°F (38°C). A normal body temperature for a human is about 98.6°F (37.0°C), and during the postpartum period, an elevation in temperature can indicate an infection. Known as puerperal sepsis, this condition can arise from an infection in various parts of the body, including the genital tract, breast, urinary tract, or a surgical wound. It is crucial to be vigilant about such infections post childbirth as they can rapidly spread and lead to severe complications like peritonitis, septicemia, and even death.