What are the legal units for measuring blood alcohol concentration?

The correct choice reflects the standard legal measurement used for blood alcohol concentration (BAC), which is expressed in grams of ethanol (ETOH) per 100 milliliters of blood. This unit provides a clear and consistent framework for legal and medical authorities to assess an individual's level of alcohol in the bloodstream. It is widely adopted in legal contexts, such as driving under the influence (DUI) cases, making it universally recognized amongst professionals dealing with alcohol impairment.

While other options present variations of measurements, they do not align with the standard legal terminology used in most jurisdictions. For example, percentage measurements might indicate alcohol content quantitatively but are not the accepted form for legal BAC definitions. Understanding the implication of these units is crucial in legal situations, ensuring clarity and uniformity in how blood alcohol levels are interpreted across various platforms such as law enforcement and judicial proceedings.