When observing someone under the influence of alcohol, what change might occur in their speech?

When someone is under the influence of alcohol, one of the common indicators is slurred speech. Alcohol acts as a depressant on the central nervous system, which can impair muscle coordination and control, including those muscles responsible for speech. This results in the person speaking in an unclear or sluggish manner, making it difficult to articulate words properly.

In contrast, options such as rapid speech or clear and concise speech would not typically be associated with alcohol consumption, as impairment generally leads to a reduction in the ability to communicate effectively. Whispered speech might occur in some situations, but it is not a general symptom associated with intoxication. Therefore, slurred speech is the most fitting change to expect when observing someone under the influence of alcohol.