What is the purpose of a VM upgrade?

• A. It solely changes the network's fee schedule globally.
• B. It upgrades the main chain's consensus rules.
• C. It removes cross-subnet messaging.
• D. A VM upgrade adds new features, fixes bugs, or improves performance and security within a subnet.

Answer: (D)

A VM upgrade is about updating the software that runs inside a subnet to improve how that subnet operates. It brings new features, fixes bugs, and can boost performance and security for that specific VM within the subnet. Because it affects only the VM running on that subnet, it doesn’t change network-wide things like the global fee schedule or the main chain’s consensus rules, and it doesn’t remove cross-subnet messaging.

So the best choice is the one that describes updating the VM to add capabilities, patch issues, and enhance efficiency and security within that subnet. The other options describe changes that involve the entire network or other mechanisms, not a subnet-level VM upgrade.