Which of the following will most likely be used in a testing environment to execute...

CompTIA A+ strongly emphasizes that virtual machines (VMs) are ideal for testing potentially unsafe software, malware samples, or experimental code because they isolate the environment from the host system. VMs allow snapshots, cloning, and rollback functionality, which makes them essential in development, QA, and cybersecurity environments where code might be unstable or harmful.

Hybrid cloud refers to infrastructure strategy, not code execution isolation. Load balancers distribute production traffic but have no testing or sandboxing purpose. Application gateways filter traffic but do not provide execution environments.

Virtual machines create a safe sandbox where failure, infection, or corruption is contained. This is covered in the Virtualization and Cloud Computing domain of the CompTIA A+ exam, making VMs the correct tool for executing unauthorized code safely.