Besides these symptoms of altitude sickness, others such as headache and fatigue may also occur.

除了这些症状外，高原反应还可能出现头痛和疲劳等其他症状。

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It may also occur among totally unrelated forms that compete for the same resource, such as seed-eating rodents and ants.

它也可能发生在完全不相关的、争夺相同资源的组织中，比如以种子为食的啮齿动物和蚂蚁。

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Additional social stresses may also occur because of the population explosion or problems arising from mass migration movements—themselves made relatively easy nowadays by modern means of transport.

由于人口的猛增或大量人口流动（现代交通工具使这种流动相对容易）造成的种种问题也会对社会造成新的压力。

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With the scene of the flight of the pagan gods at the nativity of Christ Milton is also depicting a scenario that, I think, on some level he's hoping will occur within himself.

在《圣诞清晨歌》中有一个无宗教信仰的人逃跑的画面,我认为弥尔顿同时也在描绘一个剧情，某种程度上他希望这样的事情也会发生在自己身上。

耶鲁公开课 - 弥尔顿课程节选

Vitamin B-12 deficiency anemia can also occur if your small intestine can't absorb vitamin B-12.

CNN: Vitamin deficiency anemia

Although in-hospital medication errors receive most of the attention, neighborhood-drug-store mishaps, similar to the one in Colorado, also occur frequently.

FORBES: Medication Mistakes Are A Tough Pill To Swallow

As countries become wealthier, changes in lifestyle also occur, which lead to an increase in the number of people getting cancer.

BBC: Hugo Chavez's US 'cancer plot' put to the numbers test