Final answer:
The answer is c. ultrasounds. Ultrasound imaging is the most commonly used imaging technique during pregnancy because it is considered safe for both the mother and the fetus.
Step-by-step explanation:
The answer to the question is c. ultrasounds. Ultrasound imaging is the most commonly used imaging technique during pregnancy because it is considered safe for both the mother and the fetus. Ultrasound uses sound waves to create images of the developing fetus and can provide valuable information about fetal growth and development.