b$.$ A company$-$owned mobile device is displaying a high number of ads, receiving data$-$usage limit notifications, and experiencing slow response. After checking the device, a technician notices the device has been jailbroken. Which of the following should the technician do next?

A$.$ Run an antivirus and enable encryption.

B$.$ Restore the defaults and reimage the corporate OS$.$

C$.$ Back up the files and do a system restore.

D$.$ Undo the jailbreak and enable an antivirus.