The reason that it seems difficult to say though is because it seems like it would be just as plausible to say the reverse.

但真的要说出来似乎有困难,因为反过来说也貌似合理。

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Those same estimates say that if you could turn that around, that if the world could eat the recommended level of fruits and vegetables, that you'd reduce the prevalence of heart disease by 31%.

反过来说就是,如果大家都能食用适量的水果和蔬菜,那心脏病的普遍性将降低31%

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Conversely, if you get an answer and it doesn't seem to make sense, then you've got to go back and ask, am I violating some of the assumptions, and here you will find the assumption that the particle had that acceleration a is true as long it's freely falling under gravity but not when you hit the ground.

反过来说,如果你得到一个结果,发现似乎是错的,那么你就应该回过头来问问自己,我是不是违反某些前提了,这个模型中,你就发现,只要质点在重力作用下自由下落,质点具有加速度a的前提是正确的,但是落地后就不成立了

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