Before returning to the heart, blood from the digestive tract first passes through the..
a. pancreas
b. kidneys
c. brain
d. liver

Liver

Explanation:

The hepatic portal system of liver connects the capillaries of the gastrointestinal tract to the liver. The nutrient rich blood from the gastrointestinal tract reaches the liver.

The blood that is returned back to the heart is first bought to liver and then it is returned back to the heart.

From the liver after processing the blood goes into heart for further processing.

Hence, the correct answer is option d

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