Only one can survive 只能活一个
Most people with only one copy of the gene—"carriers"—survive and pass the gene to offspring.
大多数只有一个基因拷贝的人——“携带者”——能够存活下来并将基因传给后代。
The Chukchi are used to sleep for only 4-5 hours. To survive in the peninsula one has to work nonstop.
楚科奇人习惯只睡四五个小时，为了生存他们必须不停地工作，对此他们已经习以为常了，所以几天几夜不睡觉也没问题。
And if one "manages to do it twice", does it mean the dormice choose to cross the road only once, or does it actually mean that none of them survive a second attempt at crossing the road?
如果说“有一只甚至成功穿越了两次”，那这句话是说榛睡鼠们只选择过马路一次，还是实际上除那只成功者以外，所有榛睡鼠都没能在第二次尝试中生还？
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