In general, how long does it take before an alcohol level of 1.0 per mille (100 mg/100 ml) is cleared from the blood stream?

You selected answer 1 (10 hours), which is correct. In Germany, the body usually needs about 10 hours to completely break down an alcohol level of 1.0 per mille (100 mg/100 ml) in the blood. The average breakdown rate is about 0.1 per mille per hour, although this can vary from person to person. This is why one should never rely on “sleeping off” alcohol quickly. After drinking, you may still have residual alcohol in your blood the next morning, which can affect your fitness to drive. Always give your body enough time to fully eliminate alcohol before driving.