题目内容
（请给出正确答案）
[单选题]
The difference between the mobile ISDN and MPDS is that __（）
A.the mobile ISDN is charged by connection time and MPDS is charged by data flow
B.the mobile ISDN is charged by data flow transferred and MPDS is charged by connection time
C.there is no difference between the mobile ISDN and MPDS
D.the communication fee of the mobile ISDN is cheaper than that of MPDS
答案
A、the mobile ISDN is charged by connection time and MPDS is charged by data flow
