Study Was Conducted to Look at Whether Caffeine Improves Productivity

Multiple Choice

study was conducted to look at whether caffeine improves productivity at work in different conditions.There were two independent variables.The first independent variable was email,which had two levels: 'email access' and 'no email access'.The second independent variable was caffeine,which also had two levels: 'caffeinated drink' and 'decaffeinated drink'.Different participants took part in each condition.Productivity was recorded at the end of the day on a scale of 0 (I may as well have stayed in bed) to 20 (wow! I got enough work done today to last all year) .Looking at the group means in the table below,which of the interpretations below is correct?

A) A simple effects analysis is likely to show an effect of email on productivity for decaffeinated drinks but not caffeinated ones.
B) A simple effects analysis is likely to show an effect of caffeine on productivity only for 'no email'.
C) A simple effects analysis is likely to show an effect of caffeine on productivity at both levels of email.
D) A simple effects analysis is likely to show an effect of email on productivity at both levels of caffeine.