The correct answer is A because isolating the compromised EC2 instance helps preserve its state and reduces the chance that the attacker, users, or normal production traffic will continue altering evidence before the snapshot is taken. Current AWS guidance describes incident-response and forensics workflows that isolate affected instances as part of preserving artifacts and protecting the integrity of later acquisition. AWS documentation on forensic orchestration notes that affected EC2 instances are isolated and then disk and memory acquisition actions proceed. AWS incident-response guidance also recommends isolating potentially compromised EC2 instances by associating an isolation security group. The other options happen later in the forensic workflow. Creating an evidence volume, attaching it to a forensic workstation, and provisioning an analysis host are post-snapshot or downstream examination steps. CHFI v11 includes cloud forensics and data acquisition in the cloud, so the exam logic is to stabilize and preserve the source system first, then acquire evidence from that preserved state. Therefore, the immediate step before snapshotting is to isolate the compromised EC2 instance.