numbers and percentages.
The stimulus says the number of injured children while sledding are higher than before. But the conclusion says that the percentage of injured children are higher when using plastic sled than using wooden sleds. This is a scope change. The stimulus assumes that both sleds are used in identical conditions.
To weaken the conclusion, you need to point out the above assumption is wrong. C is right.
E actually strenthens the conclusion.
-- by 会员 sdcar2010 (2011/4/17 21:13:13)