What is the system called where blood vessels originate in capillaries and end in capillaries?

$A$ portal system is a system in which

Given below are two statements regarding the circulation of blood in fishes.
Statement $I$: The heart of a fish contains only deoxygenated blood.
Statement $II$: Fishes show single circulation,and blood passes through the heart only once during each cycle.
In light of the above statements,choose the correct answer from the options given below.

The figure shows blood circulation in humans with labels $A$ to $D$. Select the option which gives correct identification of label and functions of the part.

Which of the following statements is correct regarding human circulation?

The hepatic portal vein carries blood to the liver from the ..........