Researchers suggest that humans would only survive for four years if the bees disappeared.

研究人员认为，如果蜜蜂消失了，人类就只能存活四年。

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Brain changes in the mice lasted for more than four months, equivalent to years in humans.

老鼠大脑的变化持续了至少四个月，相当于人类的好几年。

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Chimpanzees were nearly four times more likely to wait for the big reward than humans were.

大猩猩等到最大奖励的可能性比人类几乎多4倍。

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She has read the book four times. "I think if anything, this story talks about humanity and the universality of humans and how there's goodness in people and you just have to get to know one another."

VOA: special.2010.07.08

And one of the reasons that's most responsible for that is that humans aren't dying at as young an age from infectious diseases as they did three or four hundred years ago.

最重要的一个原因就是,人们不会在年轻的时候死于传染性疾病,而这在三四百年前确实会发生

耶鲁公开课 - 生物医学工程探索课程节选

Hundreds of thousands of wheels and ball bearings embedded into the floor of the facility, the lift and even the airplanes make pulling the hefty containers possible for between one and four mortal humans.

ENGADGET: Inside UPS' Worldport: How a shipping titan moves 2,000 packages every 17 seconds

The next night it's four vampires and six humans, then eight vampires and two humans.

NPR: So, What Actually Is 'Mathematically Impossible'?

The area's ecology previously had been deemed so fragile that humans were banned four months of the year.

FORBES: It's Not Easy Being Green