Several well known scientists have hypothesized that the food additive

Several well known scientists have hypothesized that the food additive monosodium glutamate – commonly known as MSG – has a negative effect on cognitive function by interfering with important neurotransmitters. A recent experiment was conducted to confirm this hypothesis: over a month period, an experimental group consumed large quantities of MSG, and a similarly sized control group did not consume any MSG. At the end of the period, the experimental group showed considerably lower cognitive abilities than did the control group.

Which of the following, if true, would best support the conclusion that MSG has a negative effect on cognitive function?

A. Most of the people who consume MSG do so in far smaller quantities than were consumed by the experimental group over the month period.

B. MSG is found naturally in many commonly eaten foods, such as mushrooms and some cheeses.

C. The cognitive function of control group was much higher than the experimental group at the beginning of the experiment.

D. The amount of MSG consumed by the experimental group over the month period was well within the limits given by the regulators.

E. The cognitive functions of the two groups were not significantly different from each other at the start of the experiment.