Word-of-mouth is the most primitive human marketing ads.

口碑，是人类最原始的行销广告。

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Any of various primitive elongated freshwater or anadromous fishes of the family Petromyzontidae, characteristically having a jawless sucking mouth with rasping teeth.

七鳃鳗，八目鳗一种七鳃鳗科的原始细长淡水或溯河产卵鱼，特点是长有无。

youdao

Any of various primitive elongated freshwater or anadromous fishes of the family Petromyzontidae, characteristically having a jawless sucking mouth with rasping teeth.

七鳃鳗，八目鳗一种七鳃鳗科的原始细长淡水或溯河产卵鱼，特点是长有无。

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