There is a small set of fast moving important change that is hard to predict -- the known unknowns .
有一小部分重要而快速的改变是难以预料到的--已知的未知数。
Why the government changed its strategy this time , and told its people what happened , remains one of many unknowns about the north .
为何此次政府改变策略,告诉人们发生的事情?这个问题仍然是众多有关朝鲜的未知数之一。
To minimize those risks while optimizing their daily operations many companies adopted management techniques such as six sigma designed to reduce the unknowns limit the uncertainties and as much as possible eliminate the risks of business operations .
Many factors , like the density of oil in undersea plumes , the size of resulting oxygen drops and the potential toxicity of oil dispersants - all unknowns - could grow into threats that outweigh any possible benefits and damage or even destroy the dark ecosystems .