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 will shave at least one-thousandth of a second off
  Question: The author says, "After all, as biomechanical machines with a standard set of parts, humans should be subject to the same limitations we in, say, automobiles. How come they aren't?" What is a good answer to this question based on the article?
  
   (A) They are subject to the same limits, just not the same quality control.
   (B) Actually, they are subject to biomechanical limitations imposed by factors like the speed at which the lungs can exchange oxygen. It's just that to date, that is not what is capping human performance potential.
   (C) It is specifically untrue that humans have a standard set of parts. There is as much variation in human anatomical details that affect running as in the difference between a Chevy truck and a race car.
   (D) Unlike inorganic automobile parts, the human machine can be improved without replacing any of its parts.
  Answer:
output: Actually, they are subject to biomechanical limitations imposed by factors like the speed at which the lungs can exchange oxygen. It's just that to date, that is not what is capping human performance potential.