Final answer:
The external fetal monitor should be placed on the mother's abdomen for accurate readings of the baby's heartbeat.
Step-by-step explanation:
The correct placement of an external fetal monitor is on the mother's abdomen. This is typically done by positioning the monitor so that it is over the area where the baby's heart rate can best be detected, which is usually above the mother's pubic bone, but the exact position can vary depending on the position of the fetus. Ultrasound technology in the monitor helps to detect the fetal heartbeat, and the monitor's belt is adjusted as needed to maintain proper contact and get the most accurate readings.