The picture shows the "pagoda of balanced diet" of China residents. Please answer according to the picture: (1) The main nutrient contained in Class A food in the picture is _ _ _ _ _ _, which is the human body. (1) The main nutrient of the first-class food in the "Balanced Diet Pagoda" is starch, which is the main energy supply for human life activities.

(2) protein is the basic substance that constitutes human cells; The growth and development of human body and the renewal of tissues are inseparable from protein; Teenagers are in a critical period of growth and development, and there is a great demand for protein. Therefore, teenagers should ensure comprehensive and reasonable nutrition, especially pay attention to the intake of protein. Therefore, they should eat more third-and fourth-grade foods in the "Balanced Diet Pagoda", which are rich in protein.

(3) The liver is the largest digestive gland in human body, and the adult liver weighs about 1.5kg, which is located in the upper right part of abdominal cavity; The liver can secrete bile, which is first stored in the gallbladder, and then enters the small intestine from the bile duct. Bile does not contain digestive enzymes, but it can emulsify fat, emulsifying large fat particles into small fat particles, and physically digesting fat, thus promoting fat digestion.

(4) Starch is first digested into maltose by salivary amylase in oral cavity, and then finally digested into glucose in small intestine; Protein is preliminarily digested into amino acids in the stomach and finally digested in the small intestine. Fat is digested into glycerol and fatty acids in the small intestine, so the small intestine is the main place for digestion. The substances that the small intestine can absorb are: glucose, amino acids, glycerol, fatty acids, water, vitamins and inorganic salts; So the small intestine is not only the main place for digestion, but also the main place for absorption.

(5) Reasonable nutrition means that the nutrients contained in the diet are complete in variety, sufficient in quantity and appropriate in proportion, and balanced with the needs of the body. The food should be diversified, the combination of meat and vegetables should be reasonable, and the nutrition should be comprehensive and reasonable. Rice mainly provides starch, fish, shrimp and chicken soup mainly provide protein and some fat, and fat meat provides fat. There are no vegetables and fruits in this recipe, which will lead to insufficient intake of vitamins and inorganic salts, so vegetables and fruits should be added.

So the answer is: (1) starch.

（2）C．

(3) liver; Bile.

(4) Small intestine.

（5）B