Belowisaselectionfromapopularsciencebook.Ifbloodisred,w...
问题详情:Belowisaselectionfromapopularsciencebook.Ifbloodisred,whyareveins(静脉)blue?Actually,veinsarenotblueataremoreofaclear,yellowishoughbloodlooksredwhenit'soutsidethebody,whenit'ssittinginaveinneart...