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 your 100-meter time. Trainers measure the rate of buildup of lactic acid
  Question: What does the author offer to refute the notion that the best current athletes will produce even better athletes in future generations?
  
   (A) Doubling up on the genes of elite athletes often leads to unexpected genetic diseases and extremes of musculature that impede athletic performance.
   (B) The human generational cycle of 20-30 years is too long for us to know yet what happens when elite athletes reproduce. It will take hundreds of years to find out.
   (C) Most athletes don't marry other athletes, so we rarely see top athletes' genes combined in their children, except for Andre Agassi and Steffi Graf - and they aren't runners.
   (D) Athletes have to train so hard for so long that they don't produce very many offspring, which is not a successful strategy for spreading their genetic material.
  Answer:
output: Athletes have to train so hard for so long that they don't produce very many offspring, which is not a successful strategy for spreading their genetic material.