撞击产生的烟尘和灰尘覆盖了地球，抑制了光合作用，引发了物种的大规模灭绝。
Airborne soot and dirt from the impact blanketed Earth, inhibiting photosynthesis and triggering mass extinction of species.
他们可以将问题旋转以更深入地覆盖不同的区域，同时仍旧保持问题列表的小规模。
They can rotate the questions to cover different areas in more depth while still keeping the list of questions small.
在非洲，受益于预防性大规模免疫运动的流行国家中达到这一覆盖水平的甚少。
Few endemic countries that recently benefited from a preventive mass vaccination campaign in Africa currently have this level of coverage.
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