下面哪些是无线网络相对于有线网络的优势()
A.维护费用低
B.安全性更高
C.可扩展性好
D.灵活度高
参考答案:A, C, D
(2013·四川,7)He is so busy.He cannot afford enough time with his son________he wants to.
A.even if
B.as if
C.because
D.before
绝缘油中三种烃类的抗氧化能力为()。
A.芳香烃>环烷烃>烷烃
B.烷烃>环烷烃>芳香烃
C.芳香烃>烷烃>环烷烃