A.一級 B.二級 C.三級
A.DC B.PICS C.CDF D.RDF
A.文獻(xiàn)數(shù)據(jù)庫 B.數(shù)值數(shù)據(jù)庫 C.事實(shí)數(shù)據(jù)庫 D.多媒體數(shù)據(jù)庫