The picture is a schematic diagram of someone's metabolism, in which A is the small intestine, B is the blood, F is the tissues and cells of the whole body, and C, D and E are the three excretory pathways of the human body. Solution: Excretion is the process that the final products of cell metabolism are excreted, such as water, inorganic salts and urea. There are three ways of excretion: first, carbon dioxide and water are excreted from the respiratory system (lungs) in the form of gas; 2. Water, inorganic salts and urea are excreted through the skin in the form of sweat; 3. Excess water, inorganic salts and urea are discharged through the urinary system in the form of urine. C is the lung, D is the kidney and E is the skin. In the picture, A is carbon dioxide, B is oxygen, C is the final product after digestion, D is sweat and E is urine.

(1) The suction pipe is a passage through which gas passes, where gas exchange does not occur. In the respiratory system, the place where gas exchange takes place is the lungs. When air enters the alveoli of the lung, because the oxygen concentration in the alveoli is greater than that in blood (whether arterial blood or venous blood), oxygen can be transferred from the alveoli to the blood without consuming energy. The concentration of carbon dioxide is higher in blood than in alveoli, so the diffusion direction is blood → alveoli.

(2) Substance A is excreted through the lungs of C, so A is carbon dioxide (CO2? ); Tissue cells continuously breathe oxygen to produce carbon dioxide and release energy to meet the needs of human life activities, so the highest concentration of substance A is tissue cells.

(3) The formation of urine is mainly through the filtration of the inner wall of glomerulus and renal capsule and the reabsorption of renal tubules. When blood flows through the glomerulus, other substances, such as water, inorganic salts, urea, glucose, etc., will be filtered into the renal capsule cavity except protein and macromolecules of blood cells, forming protourine. Therefore, compared with plasma, liquid urine in renal capsule has similar components except protein. When urine flows through renal tubules, all glucose, most water and some inorganic salts useful to human body are reabsorbed by renal tubules and return to the blood of capillaries around renal tubules. After renal tubules reabsorb urine, the remaining water, inorganic salts, urea and uric acid form urine. So D is the urinary system, which forms [e] urine. [e] Urination is a simple reflex of the nerve center in the spinal cord.

(4) The process of nutrients entering the circulatory system through the digestive tract wall is called absorption; So the process of substance [c] entering the blood circulation system from [A] small intestine is called absorption.

(5) Blood is red because it contains a red iron protein, namely hemoglobin, which is easy to combine with oxygen in places with high oxygen content; Where the oxygen content is low, it is easy to separate from oxygen; This characteristic of hemoglobin enables red blood cells to transport oxygen. When the number of red blood cells in blood is too small, or the hemoglobin content in red blood cells is too low, people will suffer from anemia. Generally, anemia patients should eat more foods rich in protein and iron. Therefore, in order to prevent the lack of protein in the body, a certain amount of food containing protein and iron should be matched when designing recipes.

So the answer is:

( 1)C； Ventilation of the lungs;

(2) carbon dioxide; Tissue cells;

(3) glomerular filtration; Renal tubular reabsorption; Simple reflection;

(4) absorption;

(5) iron.