Where does the hepatic portal system start?

Concept: The hepatic portal system comprises veins starting in the capillary beds of the stomach and digestive system and ending in the capillary beds of the Liver (liver sinusoids).
The hepatic portal system is an extraordinary and complex vascular association between the intestinal system and the liver. The veins depleting the gastrointestinal tract don't join directly with the inferior vena cava, the huge vein that returns blood to the heart.

 In the hepatic portal system blood from the spleen and digestive tract return to the liver. In the liver, blood gets cleaned before entering the heart.

Hence, option A is the correct answer.