Which of the following acronyms would indicate a common procedure for examining internal body structures?

The acronym "US" stands for "Ultrasound," which is a common medical procedure used to examine internal body structures. Ultrasound technology employs high-frequency sound waves to create images of organs and tissues inside the body. It is a non-invasive and widely used diagnostic tool that can help visualize conditions affecting abdominal organs, the heart, and even developing fetuses during pregnancy.

The other choices refer to different medical terms. "UA" stands for "Urinalysis," a test that examines urine to diagnose various conditions but does not involve imaging internal structures. "UTI" means "Urinary Tract Infection," which describes a condition rather than a procedure. "URI" stands for "Upper Respiratory Infection," which is similarly a condition affecting the respiratory system rather than a method for examining internal body structures. Therefore, "US" is the correct option as it directly corresponds to a procedure used for visualizing internal bodily structures.