(2) The small intestine is the main organ for digesting and absorbing nutrients. When blood flows through the capillaries around the small intestine, it absorbs nutrients, and blood becomes venous blood rich in nutrients. After eating, the blood in blood vessel B changed compared with that before eating, and the nutritional components increased.
(3) Arterial blood flows in hepatic artery, providing oxygen and nutrition for liver cells.
So the answer is: (1)A, B, D.
(2) The nutrients are increased.
(3) Oxygen nutrition