Over the past twenty years in the U.S., the average number of hours per week that people spend at work has increased from approximately \(41\) hours to nearly \(52\) hours. It is thought that this change has played an important role in the corresponding increase in average body mass index for working Americans over the same period. The increased time at work does not allow people as much time to exercise and engage in healthy activities that help reduce weight.

Which of the following questions would be most useful to answer in determining whether the increased workweek is an important cause of the increase in average body mass index over the past twenty years?

A. Do more employers offer healthy eating options in their onsite cafeterias today compared to twenty years ago?

B. Do more employers subsidize gym and health club memberships for their employees today compared to twenty years ago?

C. What percentage of employees use their free time to exercise and engage in healthy activities today compared to twenty years ago?

D. Did employees exercise and engage in healthy activities with the additional time when they were not at work twenty years ago?

E. What factors other than exercise and engaging in healthy activities are important for weight loss?

The OA is D