单项选择题
Thereare3stepstoconfirmwhetherarangeofIPaddresscanbesummarized.Whenofthefollowingisusedineachofthese3steps？（）
A.Thefirstnumberinthecontiguousblockofaddresses
B.Thelastnumberinthecontiguousblockofaddresses
C.Thesizeofthecontiguousblockofaddresses
D.Thesubnetmaskoftheoriginalnetworkaddress