题目选项分析

The more frequently employees take time to exercise during working hours each week, the fewer sick days they take. Even employees who exercise only once a week during working hours take less sick time than those who do not exercise. Therefore, if companies started fitness programs, the absentee rate in those companies would decrease significantly.

Which of the following, if true, most seriously weakens the argument above?

【选项】Employees who exercise during working hours occasionally fall asleep for short periods of time after they exercise.