单项选择题 WhatkindofobjectdoesthegenericDictionaryenumeratorreturn？（）

单项选择题 YouworkastheapplicationdeveloperatHi-Tech.com.YoucreateanewcustomdictionarynamedMyDictionary.ChoosethecodesegmentwhichwillensurethatMyDictionaryistypesafe？（）

单项选择题 YouworkasanapplicationdeveloperatCER-Tech.com.Cert-Tech.comusesVisualstudio.NET2005asitsApplicationDevelopmentplatform.Youaredevelopinga.NETFramework2.0applicationusedtostoreatype-safelistofnamesande-mailaddresses.Thelistwillbepopulatedallatonesfromthesorteddatawhichmeansyouwillnotalwaysneedtoperforminsertionordeletionoperationsonthedata.Youarerequiredtochooseadatastructurethatoptimizesmemoryuseandhasgoodperformance.Whatshouldyoudo？（）