Belowisaselectionfromapopularsciencebook.Ifbloodisred，w...
問題詳情：Belowisaselectionfromapopularsciencebook.Ifbloodisred，whyareveins(靜脈)blue?Actually，veinsarenotblueataremoreofaclear，yellowishoughbloodlooksredwhenit'soutsidethebody，whenit'ssittinginaveinneart...