Question

complete the text with the correct pair of words. the inferior vena cava is the largest _ in the body. in animals, _ called the caudal vena cava. vein... its vein... its vain... its vain... its

Explanation:

The inferior vena cava is a large vein in the body. "Vein" refers to the blood - vessel, while "vain" means having too high an opinion of oneself. "It's" is a contraction of "it is", which is appropriate here to say "it is called the caudal vena cava". "Its" is a possessive pronoun.

Answer:

B. vein... it's