A state of energy balance necessary for weight maintenance is characterized by:

A state of energy balance required for maintaining weight occurs when the number of calories consumed through food and drink matches the number of calories expended through bodily functions and physical activity. This balance means that the body neither gains nor loses weight, which is essential for weight maintenance.

When energy intake and expenditure are equal, the body can sustain its current weight. If a person consistently consumes more energy than they expend, they will enter a state of positive energy balance, leading to weight gain. Conversely, consuming less energy than is expended results in a negative energy balance, causing weight loss. Therefore, the ideal situation for maintaining weight is when these two factors are balanced, which aligns with the correct answer.