Answer: a. MRI
Explanation:
An X-ray machine does emit high frequency electromagnetic radiation. CT stands for Computed Tomography and it is a medical X-ray Imaging technique that uses a special kind of X-ray equipment to produce cross-sectional images of the body, so it also involves radiation. Nuclear medicine involves the usage of radioactive substances for diagnosis, research and treatment. Therefore the correct answer is MRI, a technique which stands for Magnetic Resonance Imaging, a form of test that uses powerful magnets and radio waves to obtain pictures of the inside of the body, no radiation is used.
