23.Paragraph 1 __________
24.Paragraph 3 __________
25.Paragraph 7 __________
26.Paragraph 9 __________
27.It is not so convenient to use only __________.
28.With the use of multi-service networks,users would be able to communicate with one another across __________.
29.SoftSwitch is developed by Lucent as __________.
30.From this passage we know that in the near future everyone is contacted by others through __________.