What Type of Study Is Being Conducted When Land's End

Multiple Choice

What type of study is being conducted when Land's End Home mails a catalog with a fluffy set of towels on the cover to one group of consumers and the same catalog with a cover featuring a photograph of a beautifully-made bed to another consumer group in order to test differences in response between the two groups?

A) Case study
B) Longitudinal study
C) Exploratory study
D) Experiment
E) Ex post facto study