**Core Concept**
Widmark's formula is a mathematical method used to estimate the blood alcohol concentration (BAC) based on the elimination rate of ethanol from the body. This formula takes into account factors such as sex, weight, and the percentage of body fat to calculate the BAC.

**Why the Correct Answer is Right**
Widmark's formula is specifically designed to estimate the blood alcohol level by considering the rate at which ethanol is eliminated from the body. This is achieved by calculating the amount of ethanol eliminated per hour, which is then used to estimate the BAC. The formula is based on the principle that the rate of ethanol elimination is influenced by factors such as body weight, sex, and percentage of body fat.

**Why Each Wrong Option is Incorrect**
**Option A:** Widmark's formula does not estimate the blood level of caffeine, which is a different stimulant that is metabolized by the liver.
**Option B:** Widmark's formula is not used to measure the blood level of sedatives, which are a different class of substances with distinct pharmacokinetics.
**Option C:** Widmark's formula does not estimate the blood level of anesthetics, which are potent substances that require careful monitoring.

**Clinical Pearl / High-Yield Fact**
Widmark's formula is a useful tool for forensic medicine and toxicology, as it can help estimate the BAC in cases of suspected drunken driving or other alcohol-related offenses.

**Correct Answer: C. Ethanol. Blood alcohol concentration.**