Final answer:
During a 20-minute nonstress test, three or more accelerations are considered reassuring.
Step-by-step explanation:
The correct answer is a) Three or more. During a 20-minute nonstress test, three or more accelerations are considered reassuring. An acceleration refers to an increase in the fetal heart rate, indicating a healthy response to movement. This is a positive sign of fetal well-being and suggests that the baby is getting enough oxygen.