单选题The cisco ironport portfolio performs which service?（）A reduces the downtime that is as assocoated with spam,viruses,and blended threats that are delivered via emailB defends the penmeter from malicious users and unauthorized trafficC provides A secure

reduces the downtime that is as assocoated with spam,viruses,and blended threats that are delivered via email

defends the penmeter from malicious users and unauthorized traffic

provides A secure communication path through the internet

determines if A user or device is authorized to access A switch port