The answer is D. This requires a little bit of background knowledge to answer. If you knew about places like Chernobyl, Nagasaki, or Hiroshima then you would be able to answer. In Chernobyl, a russian nuclear plant, the main reactor exploded and caused anything within an area of 2600
![km ^(2)](https://img.qammunity.org/2019/formulas/biology/high-school/zcr71dhvqdcvsx6zw4tnug09fweh8tgieb.png)
to die of serious radiation. All of Europe has traces of the radiation in the air, even America has traces of it in Chicago and other places.