1.By that time, the radioactive cloud had thinned out to such an extent that it was no longer visible.
那时，放射性云已稀释到再也看不见的程度了。
2.How was one [living in France] supposed to know whether or not to worry about a radioactive cloud?
怎能知道，[在法国生活]的人们应不应该为放射性尘埃担心呢？
3.This is considerably less than the height attained by the radioactive cloud in an air burst.
这比在空中爆炸中原子云所能达到的高度要低得多。
4.The radioactive cloud reaches a height of several miles before spreading out abruptly into a mushroom shape.
放射性云在上升达几英里高度后才猛然散开成蘑菇状。
5.The annual haze that plagues Singapore, thanks to Indonesia, is child's play compared to a radioactive cloud.
拜印尼之赐，新加坡每年都出现霾害，但与辐射云相较，只是小巫见大巫。
6.For underwater bursts at certain depths, the radioactive cloud may not be formed.
当在水下某一深度爆炸时，放射性云团也许不会形成。