Final answer:
The systemic infection characterized by symptoms like temperature instability, tachypnea, and lethargy in newborns is known as sepsis, and it is the correct answer to the student's question.
Step-by-step explanation:
The systemic infection from bacteria in the bloodstream that occurs during the first month after birth, with signs and symptoms including nasal flaring, temperature instability, tachypnea, hypotonia, lethargy, and irritability, is referred to as sepsis. Sepsis in newborns can be part of a potentially life-threatening condition known as systemic inflammatory response syndrome (SIRS). It is critically important for sepsis to be treated promptly to prevent it from advancing to shock and possible death. On the other hand, Meconium aspiration syndrome is characterized by the aspiration of meconium with the first breath, leading to breathing difficulties and potential lung complications. Respiratory Distress Syndrome (RDS) tends to affect premature infants due to insufficient production of pulmonary surfactant, while Necrotizing enterocolitis increases risk for intestinal damage and breakdown. The most appropriate answer to the question, given the symptoms described, is Answer A) Sepsis.