对于单___________个需求必须具有的基本性质：必要的、___________、可测的、___________以及可测量的。
无歧义的(或无二义的)、可跟踪的
暂无解析
Homingpigeonisusefulasa______carrierbecausewhentakenfromhome,itwillreturnatthefirstopportunity.
In1900,theenergyderivedfromburningpetroleumwasonlyfourpercent______ofcoal.
Americanseat______vegetablesperpersontodayastheydidin1910.
Manypatientsinsistonhavingwatcheswiththeminhospital,______theyhavenoschedulestokeep.