"How can I help?" That's what former Presidents George W. Bush and Bill Clinton both asked as the devastating impact of the earthquake in Haiti became clear. This question brought them to a place they
And to explain why this is so, I have a question. 为了解释为什么会是这样，我先问一个问题。 Suppose that there are two diseases: one of them is rare, the other one is common, but if they are not treated they are equally s
