"Balanced Diet Pagoda" is based on the principle of balanced diet into the approximate proportion of various types of food, and expressed in the form of a visual pagoda, in the "Balanced Diet Pagoda" in the ① layer of the food needs more, the higher the need for less, ⑤ layer, ① layer is cereals, the least amount of food needs. The least amount of food is needed in the ① layer of the "Balanced Diet Tower", the ① layer is cereals, mainly to provide energy; the ② layer of vegetables and fruits mainly to provide vitamins; the ③ layer of fish and meat, the ④ layer of milk and beans, the ③ layer, the ④ layer of the main to provide proteins and calcium; the ⑤ layer of lipids, mainly to provide fats.

(1) As can be seen, the daily intake of the most food should be the ① layer of cereals, this kind of food is rich in starch and other sugars, is the body's main source of energy, but also provides carbohydrates, protein, dietary fiber and B vitamins. Special attention should be paid to the combination of coarse and fine grains. Do not eat a single refined rice and white flour for a long time.

(2) Vitamins are not involved in the composition of human cells, but also does not provide energy for the body, and the body's need for it is very small, but it is important to the human body's various life activities. Scurvy is caused by the lack of vitamin C in the body, in the fresh vegetables and fruits contain more vitamin C.

(3) Protein is the composition of the body's cells of the basic substances; the human body's growth, development, renewal of tissues, etc. can not be separated from the protein; adolescents are in the growth and development of the critical period, the demand for protein is greater, therefore, adolescents to ensure that the nutritional aspects of a reasonable, especially to pay attention to protein intake, and to ensure that the nutritional aspects of the body's cells. Especially pay attention to the intake of protein. Diet should pay attention to more intake of food located in the pagoda layer ③ and ④, these foods can provide rich protein.

The answer is: (1) cereals; (2) ②; C; (3) ④; protein.