形象地描述一个人像运动员盯着球一样，对周围的情况保持高度警觉，能迅速且高效地做出反应。

• She’s really on the ball and noticed the mistake immediately. ^{她反应非常快，立刻就发现了错误。}
• We need a manager who is on the ball to handle this crisis. ^{我们需要一位精明能干的经理来处理这次危机。}
• You really need to be on the ball in this fast-paced job. ^{在这份节奏很快的工作中，你必须保持敏捷。}