What is the measurement uncertainty for the BrAC measurement?

The correct answer for the measurement uncertainty for the Breath Alcohol Concentration (BrAC) measurement is +/- 5% of the measured BrAC. This means that when a BrAC is measured, the actual concentration of alcohol might vary by plus or minus 5% of the measured value.

This percentage uncertainty is crucial because it helps in understanding the potential variability in results due to various factors such as instrument calibration, environmental conditions, and biological differences among individuals. It provides a statistically relevant margin that ensures the results can be trusted for legal and safety purposes, which is important in scenarios like law enforcement and public safety.

The other options present different methods of measuring uncertainty that may not align with the standards established for BrAC measurements. +/- 10% could imply a larger margin for error than is typically acceptable or standard in practice. The fixed values given in the other choices (0.005 g/210L and 0.02 g/210L) may represent specific thresholds that do not take into account the proportional variability that is better expressed through a percentage. Hence, understanding the context of measurement uncertainty in relation to BrAC and its implications is essential for accurate readings in real-world situations.