Doctors don 't know exactly what causes autism .

医生对自闭症的发病原因没有确切的看法。

Exactly how does the brain accomplish this memory processing ?

如何描述大脑完成记忆处理的准确过程？

In fact , governments have done exactly the opposite .

事实上，政府们的所作所为恰恰相反。

But that 's exactly the point .

但这就是问题的关键。

Exactly who will buy these bonds is unclear since brazilian investors can get a comparable yield without taking on so much risk .

确切地讲谁会买这些债券还不清楚，因为巴西的投资者可以获得类似的收益而同时没有冒那么大的风险。