问题补充:
the working efficiency, the boss allows the employees to have a coffee break.
A. Improving
B. To improve
C. Having improved
D. Improved
答案:
A. Improving
(答案→)B. To improve
C. Having improved
D. Improved
解析:考查不定式做目的状语,句意是:为了提高工作效率,老师允许职员喝杯咖啡休息一下。选A。