mini还是全文听写模式,很多童鞋可能进来看到【专八】可能会有点胆怯,刚开始是会感觉到有点吃力哦,但这就是专八。希望大家可以耐心的认真听写O(∩_∩)O~
In fact, the collapse played out just like a controlled demolition. To destroy a building, experts usually place explosives not just on the lowest three floors, but also on higher floors. With the top floors exploding, demolition experts can create what they call a "pancake effect", which you might realize is the same as a downward domino-effect. Unlike dominos, of course, the towers fell straight down rather than sideways. But their downfall was caused by the same forces that knock a line of dominos on their faces : Floors on the top gave in, crashing through the floors below them. As each concrete floor fell, it added force to the collapse - making it harder for each floor to hold up against the increasing pressure. Once the top floors gave way, the rest of the catastrophe was inevitable.