While there are signs that a mushroom is poisonous, they are not consistent, and all mushrooms of unknown origin should be considered dangerous to eat.

尽管有特征说明蘑菇是有毒的，但它们是不一致的，所有来历不明的蘑菇都应该被认为是有危险的食物。

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youdao

This truck is of unknown origin.

这辆卡车来历不明。

《新英汉大辞典》

The medical examiner said a contributing factor in Lee's death was "cachexia of unknown origin, " or malnutrition.

CNN: STORY HIGHLIGHTS

Unlike newspapers though, which are of unknown origin, each track in Undersound will have a birth-place, giving added meaning.

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This expulsion was instead the result of an abrupt-onset stomach ailment of unknown origin that left me doubled over in my office for most of Monday morning.

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