当光照向卡背面时，能看见一头加州棕熊的微型穿孔轮廓。
And a tiny perforated outline of a Californian brown bear is visible when a light is shone from behind.
比如，按标准技术的说法，北极熊就只是棕熊的一个变种。
The standard technique says, for example, that polar bears are just brown bears that happen to be white.
由国际科学家组成的一支研究小组发现，所有北极熊都是一种雌性棕熊的后代。
Research by an international team of scientists has found that all polar bears descend from a single female brown bear.
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