Exposure to UVB rays found in natural and artificial sunlight.

来自自然和人造阳光中的UV B射线照射。

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In some parts of the world, levels of exposure to natural radiation differ due to differences in the local geology.

在世界上的有些地区，暴露在自然辐射下的程度会因为当地的地理原因而不同。

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But the exposure is spot on, enhancing the natural glow of the evening, so the photographer should still feel very pleased with this image.

但是曝光准确无误，增加了夜晚的自然光线，所以摄影师仍应对这张照片表示满意。

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We have no idea whether this lack of natural exposure might influence how serious an epidemic of smallpox might be.

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The phenomenon has been known to laboratory scientists for many years: Rats exposed to slightly higher than natural doses of radiation live longer than ones with natural exposure.

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Australia and Canada, because of their natural-resource exposure, were hit harder and are now back to strong support from last year.

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