问一道prep上的逻辑题

foreverqueen11

Personnel officer:  The exorbitant cost of our health-insurance benefits reflects the high dollar amount of medical expenses incurred by our employees.  Employees who are out of shape, as a group, have higher doctor bills and longer hospital stays than do their colleagues who are fit.  Therefore, since we must reduce our health-insurance costs, we should offer a rigorous fitness program of jogging and weight lifting to all employees, and require employees who are out of shape to participate.  

The conclusion reached by the personnel officer depends on which of the following assumptions?

A. A person who is fit would receive a routine physical checkup by a doctor less regularly than would a person who is out of shape.

B. The medical expenses incurred by employees who are required to participate in the fitness program would be less than those incurred by employees who are not required to participate.

C. The strenuous activities required of out-of-shape employees by the program would not by themselves generate medical expenses greater than any reduction achieved by the program.

D. The fitness program would serve more employees who are out of shape than it would employees who are fit.

E. The employees who participate in the fitness program would be away from work because of illness less than would the employees who do not participate.
这道题答案选C，为什么不是B呢？B说参加这个项目的人产生的费用要小于不参加的人产生的费用，这不就说明了这个项目有助于减少医疗支出吗？麻烦各位牛牛们教教我呗，万分感谢啊！！