Which test measures the milligrams of alcohol per liter of expired air?

The measurement of milligrams of alcohol per liter of expired air is specifically associated with the Breathalyzer Test. This test uses infrared spectroscopy or fuel cell technology to accurately gauge the blood alcohol content (BAC) based on the alcohol levels in a person's breath.

When a person exhales into the device, the Breathalyzer captures the alcohol content present in the expired air and translates that measurement into a BAC figure. This method is widely used by law enforcement to assess impaired driving.

In contrast, the other options do not directly measure BAC through expired air. The Field Sobriety Test evaluates a person's physical and cognitive abilities through a series of exercises, while the Alcosensor Test is a portable device that may also assess breath alcohol content, but it's less formal than the Breathalyzer. The Kitagawa Balloon Test is used in specific contexts in Japan to detect the presence of alcohol but may not provide a precise measurement like the Breathalyzer does. Therefore, the Breathalyzer Test is the most accurate and appropriate answer for measuring alcohol concentration in expired air.