Which of the following are the important advantages that online database provides?
① The researcher can rapidly obtain a much greater variety of information than ever before
② By efficiently using online research procedures, the researcher can quickly pinpoint relevant data
③ The large in-house staff formerly required to research and maintain files can be eliminated, reducing labor costs and increasing productivity
④ Small firms can study the same secondary data as large organizations and do it just as efficiently
A.①②③
B.②③④
C.①②③④
D.①②④
正确答案是C