translation.en: The reason for that, of course, is that each of these animals produces tiny quantities, and in the case of the dog, males dogs can smell it, but we can't smell it.
translation.zh: 当然，这其中原因是 这些动物 只有一点点这种气味产生。 拿狗的情况来说， 公狗可以闻到，我们人类却不行。