Answer:
The independent variable would be the coffee.
Step-by-step explanation:
In an experiment, the independent variable is something that is added or changed by the scientist in order to see if there will be a response.
In this case, the memory test score would be the dependent variable (something that changes as a result of a change in the independent variable).
Decaf coffee could be a control group, or a group that is treated the same as the independent variable but without being exposed in order to account for any outside factors.
Finally, the type of cup used would be a constant between the control group (using the decaf coffee) and the experimental group (the group with regular coffee).
Hope this helps!