on the ball

汉语翻译

例句：

1. The new clerk is really on the ball. He's already improved the filling system in the office.
   新来的办事员真能干，他已经改进了办公室文件归档的方法。
2. If you don't get on the ball and start studying harder, you're going to flunk.
   如果你不积极进取，更加努力学习，你就会考不及格的。
3. The new publicity manager is really on the ball.
   新的宣传部主任确实很内行。
4. The great value of Jack as a committee man is that he is always on the ball.
   作为一名委员，杰克的巨大作用是始终保持警惕。