文件外壳型病毒(55)。

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For　each　blank,　choose　the　best　answer　from　the　four　choices　and　write　down　on　the　answer　sheet.Web　browser　is　simply　a　terminal　emulator,　designed　to　display　text　on　a　screen.　The　two　essential　differences　between　an　ordinary　terminal　emulator　and　a　Web　browser　are　that　the　browser　knows　how　to　deal　with(71),　and　that　it　has　a　mechanism　for(72)graphical　files.　Display　text,　display　graphics,　and(73)hyperlinks—there's　99　percent　of　the(74)value.　That's　not　to　say　that　the　manufacturers　didn't　go　all-out　to　attach　a　hyperactive　efflorescence　of　useless　capabilities　onto　their　browsers.　Remember　when　media　channels　in　the　browser　were　a　big　deal,　instead　of　the　clutter　you　can't　wait　to　delete　from　your　favorites　of　bookmarks　menu?　Remember　when　client-side　Java　applets　were　supposed　to　become　the　preferred(75)for　application　development?　Remember　frames　and　all　their　nasty　side　effects?

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For　each　blank,　choose　the　best　answer　from　the　four　choices　and　write　down　on　the　answer　sheet.

(66)is　a　one-way　function　that　takes　an　arbitrarily　long　piece　of　plaintext　and　from　it　computes　a　fixed-length　bit　string.

(67)is　a　protocol　that　most　USENET　machines　now　use　it　to　allow　news　articles　to　propagate　from　one　machine　to　another　over　a　reliable　connection.

(68)is　an　approach　preferred　by　cable　TV　providers.　In　this　solution　the　fiber　terminates　at　an　optoelectrical　converter　and　the　final　segment　is　a　shared　coaxial　cable.

(69)is　a　device　used　to　connect　two　separate　network　that　use　different　communication　protocol.

(70)is　a　digital-to-digital　polar　encoding　method　in　which　the　signal　level　is　always　either　positive　or　negative.