Which combining form corresponds to blood vessels?

The combining form that corresponds to blood vessels is "vas/o." In medical terminology, the prefix "vas-" comes from the Latin word "vas," which means vessel. This form is commonly used in various medical terms that relate to blood vessels, such as "vasodilation" (the widening of blood vessels) and "vasculitis" (inflammation of blood vessels). Understanding combining forms can be very helpful in deciphering complex medical terms related to the circulatory system and vascular health.

The other choices represent different body systems or parts: "path/o" refers to disease, "proct/o" pertains to the rectum, and "rhin/o" relates to the nose. Therefore, "vas/o" is specifically aligned with the context of blood vessels, making it the correct choice.