单项选择题

D

A long-range health study in Framingham, Massachusetts, which began in 1948 and continues to this day, involves checking those who remain alive among the same 5 200 men and women every two years and carefully determining the causes of any deaths occurring in the group. A rather astonishing conclusion that became known in 1980 was that the lightest men had the shortest life expectancy (预期寿命) while the only others for whom weight seemed to have a significant (有意义的，重要的) opposite effect on life expectancy were those who weighed more than 25% above the national average. Much the same was true of women, with those in the lightest and heaviest groups dying earliest. These results certainly threw many doubts on the validity (有效性) of the Ideal (理想的) Weights tables in use since the forties which speak in favor of weight to height ratios (比率) well be low the national average. Indeed, they suggest that if any such idea] exists, it is slightly above the average, whatever fashion may be.

The author of the passage thinks that______.