A manager has noticed that her workers are more likely to be in negative moods between 3 pm and 4:30 pm. She believes that employees will make valuable contributions to staff meetings when they are in positive moods, and those staff meetings cannot be successful unless the employees make valuable contributions. For these reasons, she has moved her daily staff meeting from 3 pm to 10 am. If the manager's statements are all true, which of the following must also be true?

A. The meetings would be more effective if they were held once a week.
B. The staff meetings are not the cause of the workers' bad moods.
C. If the workers make valuable contributions, then the meetings will be successful.
D. Successful meetings will be an important contributor to the success of the organization.
E. The workers' moods will be more positive at 10am than at any other time of the day