题目

混合气体由N2和CH4组成，测得混合气体在标准状况下的密度是0.821g/L，则混合气体中N2和CH4的体积之比为（    ） A．5∶1      B．1∶4        C．4∶1         D． 1∶5   答案：B13、一I saw Ann _______ a green dress at the school meeting． 一I think she looks better _______ red． A．dressed；in          B．put on；wear           C．wearing；in               D．wear；put on