input: Text: The Olympic Gene Pool Why the human race keeps getting faster. By Andrew Berry ( 2,168 words; posted Thursday, July 4; to be composted Thursday, July 11 ) On May 6, 1954, at Oxford University's Iffley Road track, Roger Bannister became, by just half a second, the first man to run a mile in less than four minutes. The Holy Grail of middle-distance running was his. Forty-two years later, however, that achievement seems less significant. Four-minute miles are commonplace; the current record, held by Algerian Noureddine Morceli, is 3:44, more than 5 percent faster than Bannister's speed. What Iffley Road witnessed was just another step along the road to an ever quicker mile, part of the inexorable improvement of athletic performance that we usually take for granted, particularly when the Olympics roll around. If you stop to think about it, though, such constant progress is remarkable. After all, as biomechanical machines with a standard set of parts, humans should be subject to the same limitations we see in, say, automobiles. How come they aren't? A lot of entrepreneurs and technophiles would like us to think that the answer has to do with discoveries in the world of sports technology. A new Nike shoe is trumpeted as something that
  Question: According to the author, the age of onset of girls' periods is an indicator of improved diet, one factor in the improved health conditions correlated with humans running faster. That being the case, what group might be expected not to have had much improvement in their athletic performance in the last hundred or so years, based on what happened to their age of onset of periods during that time?
  
   (A) The upper crust of society, people who already and always had enough money to remain well-fed, and therefore already performed better, and did not stand to gain as the general level of nutrition improved.
   (B) People who experienced cycles of good and bad fortune would have only benefited a little from society's improved health conditions.
   (C) People of average economic circumstances have continued to have average economic circumstances, therefore their health did not improve, and athletes from this social stratum have not improved.
   (D) Girls were not allowed to compete in athletic events at the time, so no one really knows whether improving nutrition helped their speed.
  Answer:
output: The upper crust of society, people who already and always had enough money to remain well-fed, and therefore already performed better, and did not stand to gain as the general level of nutrition improved.