国内有网易公开课、腾讯课堂、百度传课等非常优秀的网课平台，而在国外也有很多非常优秀的在线网课平台，比如：Riboflavin is necessary as a way to sort the purple blood cells as well as antibodies within the human beings that help in oxygenation and circulation with the organs in the human body. (8)Even