Why not D?

Why is answer choice D incorrect? Surely it highlights a discrepancy between the study and consumers' real-life experience: in the study the volunteers may prefer Sparkle Cola because they were only exposed to taste, whereas in real life consumers may prefer other colas because of other factors (eg packaging)? Therefore, since the study's conditions are unrealistic, we can't extrapolate from its results a general principle that consumers prefer Sparkle Cola.