单项选择题
（）statementcanperformacalculationandstoretheresultinavariablesothatitcanbeusedlater.
A.Assignment B.Control C.I/O D.Declaration
单项选择题 Dataitemsareaddedordeletedfromthelistonlyatthetopofthe（）.
单项选择题 （）meansthataprogramwrittenforonecomputersystemcanbecompiledandrunonanothersystemwithlittleornomodification.
单项选择题 （）hasbecomeafactofmodemlife，withmillionsofpeoplenowshoppingon-line.
