Match the diet reasonably and pay attention to the health of the diet. Please use the chemical knowledge you have learned to answer the following questions: (1) It is best to have rice (or steamed bread) in every meal. (1) Rice contains a lot of starch, which belongs to sugar, and fish is rich in protein.

(2) Vegetables are rich in vitamins, which can regulate metabolism, prevent diseases and maintain health. Without vitamins, it is easy to get sick, such as night blindness without vitamin A and scurvy without vitamin C;

(3) The function of potassium fertilizer is to strengthen the stem and strengthen the lodging resistance and pest resistance of vegetables.

So the answer is:

(1) sugar (class) and protein;

(2) regulating metabolism, preventing diseases and maintaining good health (or regulating metabolism);

(3) Potash fertilizer.