To determine Blood Alcohol Concentration (BAC) for a person, it is necessary to know?

To determine Blood Alcohol Concentration (BAC) for a person, knowing how much that person weighs is essential because body weight directly influences the level of alcohol concentration in the bloodstream. Generally, a person's BAC increases as they consume alcohol, but the effect of alcohol can vary greatly depending on body weight. Heavier individuals tend to have a lower BAC for the same amount of alcohol consumed compared to lighter individuals, as the alcohol is distributed in a larger volume of body fluid. This factor is crucial for accurately assessing how alcohol impacts an individual's ability to operate a vehicle safely.

The other factors, while they can influence a person's response to alcohol, do not provide a direct measure needed to calculate BAC. For example, tolerance levels are more about how the body reacts to alcohol over time rather than a direct calculation of BAC. A person's age can influence their metabolism and how quickly they process alcohol, but this is not a primary factor needed to calculate BAC. Lastly, the time that has passed since the last drink affects BAC but doesn't play a part in determining the actual concentration level at a given moment. Therefore, an individual's weight is the key piece of information required to calculate BAC accurately.