The next step after isolating the system is to perform a system scan to remove the malware (Option C).
Since ransomware is suspected, running a comprehensive malware scan can help identify and remove the malicious software. It is crucial to deal with the active threat before taking further actions.
* Scheduling an antivirus scan and system update (Option A) may help, but the immediate concern is identifying and removing the ransomware.
* Educating the end user (Option B) is important but should happen after the immediate threat is resolved.
* Creating a system restore point (Option D) would not be useful at this point since the system is infected.
CompTIA A+ Core 2 References:
* 2.3 - Detect, remove, and prevent malware, including handling ransomware.