Which of the following types is used by computed tomography employed for visualization of the internal structure of human body?

Computed tomography (CT) is an X‑ray–based tomographic technique that acquires multiple X‑ray projections around the body and reconstructs them into cross‑sectional images; CT therefore uses ionizing X‑radiation to produce slices of internal anatomy [1]. The historical and technical naming also reflects this: CT was developed as X‑ray computed tomography (credit to Hounsfield) and is routinely described under X‑ray imaging modalities [2]. Other options are modalities different from CT: ultrasound uses sound waves, MRI uses magnetic fields and radio waves, and radioisotope techniques (PET/SPECT) use radioactive tracers and gamma emissions. Hence the correct choice is X‑rays.

Sources

1. [1] https://www.sciencedirect.com/topics/computer-science/imaging-modality
2. [2] https://www.utsouthwestern.edu/edumedia/edufiles/education_training/programs/stars/arbique-medical-imaging.pdf