What is population distribution? The number of individuals per unit area
The number of males and females of each age a
population contains
How individuals are spaced out across the range of the
population
The area inhabited by a population

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.