A sandbox in virtualization allows testing an application in an isolated environment to observe its behavior without affecting the host system. * Why Not A (Run an application on multiple workstations): This describes application virtualization, not sandboxing. * Why Not C (Migrate a legacy application): This is about virtualization for legacy support, not testing. * Why Not D (Create a firewall): A firewall does not act as a sandbox for application testing. CompTIA A+ Exam Reference: Core 1 (220-1101), Section 4.2, virtualization and sandboxing.