四百年前，这个数量就超过了五亿。
四百年前，明朝地理学家、文学家徐霞客在旅途中度过了三十多年。
Xu Xiake, a geographer and writer in Ming dynasty, spend more than thirty years on the road four hundred years ago.
四百年前的一个苹果带来了万有引力定律，而史蒂夫有·乔布斯设计的苹果大大地改变了我们的生活。
An apple four hundred years ago led to the law of gravity while the apple designed by Steve Jobs has changed our life greatly.
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