CR200这道题为什么选E啊，求大神们解答

Psychiatrist: an analysisof psychological and health data collected onalmost 100,000 individuals found that during an eight-year period, thosewho were especially cheerful andoptimistic had 30 percent lower risk of heartdisease than those who were pessimistic. This shows that many peoplecould improve their healthy by deliberately cultivating an optimistic attitude.

The psychiatrist’sargument is most valuable to criticism on which of the following grounds?

A It fails to adequatelyaddress the possibility that several factors in addition to an optimistic orpessimistic attitude affect the risk of heart disease.

B It takes for grantedthat lowering the risk of heart disease is the most effective way to improve overall health.

C It reaches a generalconclusion about the population as a whole based on a sample that is not representative of that population incertain relevant respects.

D It assumes that what istrue of a certain span of time is also true of a longer span of time.

E It concludes, withoutsufficient evidence, that a certain causal relationship accounts for thecorrelation between two factors.

感觉每个选项都有道理，为什么偏偏选了E呢？

求大神解答！感激不尽！