题目

Do you hope to enter Tsinghua University? If so,you’d better be able to swim or be ready to learn swimming and pass a swim test,because all the students of Tsinghua University are asked to learn how to swim from this year. Liu Bo,head of the university's sports science and physical education division,said this last Monday and this decision was most supported by Qiu Yong,president of this university. The university will organize a swimming test for all the new students in September,and those who fail to swim at least 50 meters any way they like will be asked to take a mandatory course 试管中盛有黑色粉末，将其加强热，粉末变为红色，同时产生无色气体，该气体能使澄清的石灰水变浑浊，则该黑色粉末可能是（　　）A．木炭粉B．四氧化三铁C．氧化铜D．木炭粉和氧化铜