Which of the following is considered a sign of intoxication?

Slurred speech is a common and noticeable sign of intoxication. When a person consumes alcohol, it affects their central nervous system, impairing motor skills and coordination. This impairment tends to manifest in speech, making it difficult for individuals to articulate their words clearly. As blood alcohol content increases, the clarity and coherence of speech diminish, leading to slurred or mumbled phrases.

The other options indicate opposite effects typically associated with sobriety. Increased energy can occur in social situations but does not reliably indicate intoxication, as some individuals may seem energized without being under the influence. Quick reactions and clear thinking are also traits of sobriety — as alcohol consumption generally leads to slower reaction times and a muddled thought process. Therefore, slurred speech stands out as a definitive sign of alcohol intoxication.