多项选择题
WhichtwostatementsabouttheuseofSCREENoptionsarecorrect？（）
A.SCREENoptionsaredeployedattheingressandegresssidesofapacketflow.
B.AlthoughSCREENoptionsareveryuseful，theirusecanresultinmoresessioncreation.
C.SCREENoptionsofferprotectionagainstvariousattacksattheingresszoneofapacketflow.
D.SCREENoptionsexaminetrafficpriortopolicyprocessing，therebyresultinginfewerresoucesusedformaliciouspacketprocessing.