Critical Reasoning

Exposure to certain chemicals commonly used in elementary school as cleanser or pesticides causes allergic reactions in some children. Elementary school nurses in Renston report that the proportion of school children sent to them for treatment of allergic reactions to those chemicals has increased significantly over the past 10 yrs. Therefore, either Renston's school children have been exposed to greater quantities of the chemicals, or they are more sensitive to them than school children were ten yrs ago.
Which of the follow. is an assumption on which the argument depends?
A) The no. of school nurses employed by Renston's elementary school has not decreased over the past 10 yrs.

B) Children who are allergic to the chemicals are no more likely than other children to have allergies to other substances.

C) Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were 10 yrs ago

D) The chemicals are not commonly used as cleanser or pesticides in houses and appt. buildings in Renston.

E) Children attending elementary school do not make up a larger proportion of Renston's population now than they did 10 yrs ago.

Argument: More cases of elementary School Children being sent to nurses.
Conclusion - Above due to 2 probable reasons: 1. Either exposed to increased quantities of chemicals or 2. children have become more sensitive to the same quantity of chemicals to which they are exposed.
what must be assumed for the argument to hold water above. that children are NOt MROE LIKELY to be sent to nurses now than 10 years before. If we negate this, and CHILDREN ARE increasingly sent to nurses than 10 years before, then it provides an alternate cause of why the increase in number being sent to nurses (rather than increased sensitivity of children or increased quantity of chemicals). which kind of breaks the logical flow of arument / breaks the argument.
If we negate an assumption, the argument must break and its happening if we negate C.
hence assumption must be C.

i vote for C

The OA is C

This is an assumption question, it is also a cause and effect question. The effect that has been observed and cannot be contradicted is that more children are going to the school nurse. Now the speculation is about the cause. The conclusion says that the cause is either "children have been exposed to greater quantities of the chemicals, or they are more sensitive to them than school children were ten yrs ago."

So, in order for that to be the cause, we are assuming that we do not have a more logical or compelling cause. Choice C mentions a possible alternative cause and then assures us that it is not present. "Children who have allergic reactions to the chemicals are not more likely to be sent to a school nurse now than they were 10 yrs ago."

This question was also discussed at this link:
https://www.beatthegmat.com/assumption-q ... 13740.html

IMO C.