A large group of hyperactive children whose regular diets included food containing large amounts of additives was observed by researchers trained to assess the presence or absence of behaviour problems. The children were then placed on a low-additive diet for several weeks, after which they were observed again. Originally nearly 60 percent of the children exhibited behaviour problems: after the change in diet, only 30 percent did so. On the basis of these data, it can be concluded that food additives can contribute to behaviour problems in hyperactive children.

The evidence cited fails to establish the conclusion because

A. there is no evidence that the reduction in behaviour problems was proportionate to the reduction in food-additive intake

B. there is no way to know what changes would have occured without the change of diet, since only children who changed to a low-additive diet were studied

C. exactly how many children exhibited behaviour problems after the change in diet cannot be determined, since the size of the group studied is not precisely given

D. there is no evidence that the behaviour of some of the children was unaffected by additives

E. the evidence is consistent with the claim that some children exhibit more frequent behaviour problems after being on the low-additive diet than they had exhibited when first observed

I would go with 'B'

Also go with B.

A. strengtheten the argument.
B. weakens the conclusion..........correct.
C. out of scope.
D. supports the conclusion.
E. also supports.

one more for B.

OA is 'B'