Final answer:
After the initial physical assessment, the nurse should determine the blood glucose level of the newborn.
Step-by-step explanation:
After the initial physical assessment of a newborn with a cesarean birth due to cephalopelvic disproportion and Apgar scores of 7 at 1 minute and 9 at 5 minutes, the nurse should determine the blood glucose level (option B). This is important because babies born by cesarean section are at a higher risk of having low blood glucose levels. Administering oxygen by hood (option A) is not indicated based on the provided information. Passing a gavage tube for a formula feeding (option C) and transferring the newborn to the neonatal intensive care unit (option D) are not necessary based on the Apgar scores and the absence of other indications for such interventions.