## Core Concept
The core concept being tested here is the legal definition of intoxication based on blood alcohol concentration (BAC). BAC is measured as the grams of alcohol per deciliter of blood (g/dL) or milligrams per milliliter (mg/mL), often expressed as a percentage.

## Why the Correct Answer is Right
The correct answer, **0.08% (80 mg/dL)**, is widely recognized as the threshold for intoxication in many jurisdictions. At this concentration, an individual's ability to operate a vehicle or perform other tasks is significantly impaired. This level is determined through studies of alcohol's effects on psychomotor skills and cognitive functions. The mechanism involves alcohol's action on the central nervous system, affecting neurotransmitter systems that regulate mood, behavior, and motor control.

## Why Each Wrong Option is Incorrect
- **Option A: 0.05% (50 mg/dL)**: This level is considered to be under the influence but not necessarily intoxicated in the legal sense in many places. However, effects can vary widely among individuals, and even at this level, impairment can occur.
- **Option B: 0.10% (100 mg/dL)**: While clearly above the threshold for intoxication, this option is not the standard legal limit in many jurisdictions.
- **Option D: 0.15% (150 mg/dL)**: This is well above the legal limit for intoxication and represents a level at which severe impairment is likely.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the legal limit for intoxication varies by jurisdiction but **0.08% (80 mg/dL)** is a commonly accepted threshold in many countries, including the United States. Additionally, individual tolerance, body weight, and the rate of alcohol consumption can significantly affect the level of impairment.

## Correct Answer: C. 0.08% (80 mg/dL).