Which of the following statements about the secondary use of personal information is correct?

A、Secondaryuseistheuseofpersonalinformationforapurposeotherthantheoneforwhichthepersonsuppliedit.;
B、Transferthepersonalinformationprovidedbytheuseratthetimeofregistrationtoothercompanies.Thisisakindofsecondaryuse.;
C、Thecommontechnologiesinvolvedinthesecondaryuseofpersonalinformationincludedataminingandusercharacteristicsanalysisetc.;
D、Theseconduseofuser'spersonalinformationonthenetworkplatformiscompletelyunnecessaryforuserstoknow.