GMAT Critical Reasoning (CR) | Studies have shown that children who watch a lot of television do not

The argument is saying watching more television leads to decrease in grade level. It is based on the study done on American and western children.

So, the assumption should be other conditions were same on those children. It was just the TV viewing duration.

This is what option E is doing. It is saying there was no other change in teaching methods. Hence, an assumption.

(A) American children are not as interested in reading well as children in other western countries. : ok, so there are not
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