Final answer:
An X-ray uses electromagnetic radiation to view internal structures and is the correct answer. Other modalities like CT scans also use electromagnetic radiation, while MRIs and PET scans use different technologies. Ultrasounds are safest for use during pregnancy.
Step-by-step explanation:
The diagnostic study that uses electromagnetic radiation to view internal structures is an X-ray. X-rays are a form of electromagnetic radiation that can pass through the body, allowing images of the bones and certain organs to be captured. Other diagnostic studies mentioned include CT scans, MRI, and PET scans, each using different methods to create images of the body. For example, CT scans also use electromagnetic radiation, while MRIs use magnetic fields and radio waves, and PET scans use a radioactive substance to show how the body's cells are functioning.
When it comes to safe imaging during pregnancy, ultrasounds are considered the safest because they do not use ionizing forms of electromagnetic radiation. This makes ultrasounds the preferred method for monitoring the development of the fetus.