Other experts, however, believe this temperature trend is a natural variation.
但是另外一些科学家却认为这种温度变化趁势是自然变化。
But even among the smartest bird species, there's still natural variation in brain size.
但是，即使是最聪明的鸟类，它们的大脑尺寸也存在自然变化。
Natural color variation may occur in this product.
天然颜色变化可能发生在这个产品。
Natural color variation may occur in this product.
天然颜色变化可能发生在这个产品。
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