(2) The first floor of the Balanced Diet Pagoda is cereals, which mainly provide sugars such as starch and can provide energy.

(3) protein is an indispensable substance in human tissues, and it is also the main component of various enzymes, antibodies and some hormones. Children and adolescents are in the critical period of physical growth and development, so they should supply more protein to ensure their growth and development, so they should eat more food in the third and fourth floors of the pyramid.

(4) Food contains six nutrients that the human body needs. In addition, food also contains a kind of substance, which can neither be decomposed by digestive enzymes in the body nor absorbed by the body, but it is necessary to maintain health. In nutrition, this kind of substance is called dietary fiber. In view of the close relationship between dietary fiber and human health, some scholars rank it after the six nutrients and call it the seventh nutrient.

So the answer is: (1) water, inorganic salts?

(2) Starch (or sugar)? energy

(3) protein? Three, four

(4) Dietary fiber