Which statement is a valid explanation as to why black-box test design techniques can be useful?

A、Theycanhelptoderivetestdatabasedonanalysisoftherequirementspecification
B、Theycanhelpderivetestcasesbasedonanalysisofacomponentcodestructure
C、Theycanhelptoderivetestconditionsbasedonanalysisofasysteminternalstructure
D、Theycanhelptoreducetestingcosts