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. vane... its vein... its vane... its vein... its

Explanation:

1. For the first blank: "vein" refers to a blood vessel, while "vane" is part of a feather or a blade in a turbine, etc. The inferior vena cava is a blood vessel, so "vein" is correct.
2. For the second blank: "It's" is a contraction of "it is", and "its" is a possessive pronoun. Here we need "it is" (contracted as "It's") to say that in animals, (the inferior vena cava) is called the caudal vena cava. So the correct pair is "vein... It's".

Answer:

D. vein... It's