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 in your muscles, then claim that their programs will control it. Nutritionists fine-tune athletes' diets. Even the old sexual-abstinence-before-the-race dogma is being re-e
  Question: What does the author put forward as the main reason why British athletes win fewer Olympic medals than at the beginning of the 20th century?
  
   (A) As the British Empire gradually collapsed, Great Britain became less wealthy, and competing in the Olympics is expensive.
   (B) The British have been weakened by the introduction of many, many foreigners into the UK.
   (C) The British lost their toughness, and hence their athletic advantage, when life got too easy for them.
   (D) The number of countries and number of athletes competing has risen dramatically over time. There is a much bigger pool of potential winners.
  Answer:
output: The number of countries and number of athletes competing has risen dramatically over time. There is a much bigger pool of potential winners.