几千年来这两种物质的数量都是一样的，可人类进行原子弹测试的二十年大气中碳十四的含量增加了。 For thousands of years, the ratio between the two has been the same. But those two decades of atomic bomb tests increased the C-14 in the atmosphere.
尽管在英国与澳大利亚最为重要且出名的经济损失案例也都只是集中于过去的二十年中，但这些案例在学术研究上却都起到了里程碑的作用。 Although, most important cases were mentioned in the past two decades in England and Australia. But these cases also are the significant literature in the world.
他们中有些都跟了我们二十年了。 Some of our employees have been with us for twenty years.
但是，爷爷，她说，你几乎每天都去那个公园已经二十年了，你怎么会在那里迷路呢？ But, Grandfather, she then said, you have been to that park nearly every day for twenty years. How did you lose your way there?