Renal portal system of frog is significant in
A. Quick short circuit for elimination of nitrogenous wastes
B. Supplying extra blood to kidneys
C. Drawing blood from kidneys
D. Quick short circuit for elimination of fats

Hint: As we know that blood flows in a certain pattern and in veins or capillaries so, an arrangement in which blood are collected from one set of capillaries by a vessel to another set of capillaries is known as portal system. There are three types of portal system – hepatic portal system, hypophyseal portal system, renal portal system.

Complete answer:
As we know, the Renal portal system- renal portal system is a venous portal system which is present in all living vertebrates except mammals, hagfish and lampreys. Renal portal system consists of renal portal vein and capillary network.
The renal portal vein is developed from the posterior cardinal vein.
It brings out the venous blood from the kidney where it passes through a shunted capillary network and convoluted tubules. then the blood enters the posterior cardinal vein or posterior vena cava.
The Renal system carries blood from kidney to heart in lower invertebrates. They perform a systemic circulation which helps in proper blood flow in the body.
Frog's hind limbs are the busiest organs. The blood coming from the hind limbs are considerate to have more metabolic wastes so, through the renal portal system this blood comes into kidneys. The renal portal system forms a network of blood capillaries around the uriniferous tubules of the kidney.
In frogs, the elimination of the nitrogenous wastes and blood purification can be carried out by the portal system and the kidneys. Each kidney is composed of several uriniferous tubules called nephrons. The frog excretes urea and thus is a ureotelic animal.

So, it is a Quick short circuit for elimination of nitrogenous wastes

Note:
So, we discussed the Portal system as an arrangement of a system which helps in blood purification, hormones signaling, transportation of messages from different organs into the heart and parts of the brain. It regulates the mechanism of the body well. As we know, it carries venous blood to be filtered out in the kidney before moving back to heart. It also has sets of tributaries capillaries.