2012年11月1号新加坡GRE机经回忆

　　issue：People's behavior is largely determined by forces not of their own.
　　argu 46: The following appeared in a health magazine published in Corpora."Medical experts say that only one-quarter of Corpora's citizens meet the current standards for adequate physical fitness, even though twenty years ago, one-half of all of Corpora's citizens met the standards as then defined. But these experts are mistaken when they suggest that spending too much time using computers has caused a decline in fitness. Since overall fitness levels are highest in regions of Corpora where levels of computer ownership are also highest, it is clear that using computers has not made citizens less physically fit. Instead, as shown by this year's unusually low expenditures on fitness-related products and services, the recent decline in the economy is most likely the cause, and fitness levels will improve when the economy does."
　　Write a response in which you examine the stated and/or unstated assumptions of the argument. Be sure to explain how the argument depends on these assumptions and what the implications are for the argument if the assumptions prove unwarranted.