[单项选择]People who work in emergency services must be ready ______ at a moment's notice.
A. act
B. acting
C. acted
D. to act

Nowadays, people work longer hours than they used to, but are they really working harder than ever before Apparently, many people believe that the more time a person spends on work, (21) she or he accomplishes. However, the connection between time and (22) is not always (23) . In fact, many studies indicate that after a certain point, anyone’s productivity and creativity begin to (24) . Furthermore, it is not always easy for individuals to (25) that their performance is falling off.
Part of the problem is understandable. When (26) evaluate employees, they often consider the amount of time spent on the job (27) performance. Employees know this. Consequently, they work longer hours and (28) less vacation time than they did several years ago. Although many working people can do their job effectively during a (29) 40-hour-work week, they feel they have to spend more time on the job after normal working hours
A. production
B. product
C. productivity
D. productive