The correct option is A One
The circulatory system found in frogs is of closed type. In this type of circulation, the blood is pumped by heart through vessels. The blood from heart is carried to all parts of the body by arteries and the veins collect blood from different parts of the body to the heart. Blood supplies nutrients and oxygen to all parts of the frog's body .
Special venous connection between liver and intestine as well as the kidney and lower parts of the body is present in frogs. The former is called hepatic portal system and the latter is called renal portal system. The hepatic portal system is a series of veins that carry blood from the capillaries of the alimentary canal to capillaries in the liver. Renal portal veins carry blood from the posterior parts of the body to the kidneys.
Since options i and iii are incorrect, the correct answer is option a.