What is a common effect of driving under the influence of alcohol?

Driving under the influence of alcohol significantly impairs an individual’s abilities, with decreased reaction time being one of the most critical effects. Alcohol slows down the central nervous system, affecting the brain's function and the ability to process information quickly. When a driver consumes alcohol, their physical and mental responses are delayed, making it difficult to react promptly to changing conditions on the road, such as the sudden appearance of obstacles or the actions of other drivers. This impairment can lead to serious accidents, as timely responses are essential for safe driving.

In contrast, the other options suggest effects that are not associated with alcohol consumption. Improved decision-making skills, enhanced concentration, and increased energy levels are all outcomes that would typically be associated with optimal cognitive function. When under the influence, however, alcohol disrupts these abilities rather than improving them, illustrating the dangers of impaired driving.