Half of the subjects in an experiment-the experimental group-consumed large quantities of a popular artificial sweetener. Afterward, this group showed lower cognitive abilities than did the other half of the subjects-the control group who did not consume the sweetener. The detrimental effects were attributed to an amino acid that is one of the sweetener' s principal constituents. Which of the following, if true, would best support the conclusion that some ingredient of the sweetener was responsible for the experimental results?
A: The two groups of subjects were evenly matched with regard to cognitive abilities prior to the experiment.
B: A second experiment in which subjects consumed large quantities of the sweetener lacked a control group of subjects who were not given the sweetener.
C: The amino acid referred to in the conclusion is a component of all proteins, some of which must be consumed for adequate nutrition.
D: Most consumers of the sweetener do not consume as much of it as the experimental group members did.
Choose A, B, C or D as your solution.
A