根据下面的文字资料回答 68~72 题
For each blank.choose the best answerfrom the four choices and write down on the answer sheet.
( 1 )is a protocol that a host uses toinform. a router when it joins or leaves an Internet muhicast group.
( 2 ) is an error detection code that most data communication networks use.
( 3 )is an interior gateway protocol that uses a distance vector algorithm topropagate routing information.
( 4 )is a transfer mode in which all types of information ate organized intofixed form. cells onan asynchronous or non-periodic basis over a range of media.
( 5 )is an identifier of a web page.
第68题:文中( 1 )处正确的答案是( )。