Final answer:
The nurse would expect to find the top of the fundus at the midline and 1 cm below the umbilicus at the end of the first postpartum day, indicating option c) 2 cm below the umbilicus is the correct position.
Step-by-step explanation:
At the end of the first postpartum day, a nurse assessing the position of the uterus would expect to find the top of the fundus at the midline and 1 cm below the umbilicus. After childbirth, the uterus begins a process known as involution, where it contracts back to its pre-pregnancy size. This process is quite rapid immediately after birth, with the uterus typically descending into the pelvis by about one centimeter, or about the width of a finger's breadth, per day. Therefore, the correct answer to the question would be option c) 2 cm below the umbilicus.