IaaS volume storage encryption protects from which following security risk(s)?

A alone is incomplete because volume encryption also protects against unauthorized viewing by provider employees when customer-managed keys are in use.

Volume encryption does not prevent a volume from being moved to another region or physical host - the provider's control plane can migrate it regardless of encryption state.

C alone is incomplete because volume encryption also protects against data exposure through snapshot cloning or accidental snapshot sharing.

Both A and B is incorrect because B - protection from volume movement - is not a capability that storage encryption provides.

Encryption protects against snapshot cloning/exposure (A) because any cloned or leaked snapshot remains unreadable ciphertext without the decryption key. It also protects against cloud provider employee access (C) when customer-managed keys are used, as provider personnel cannot decrypt data they do not hold the key for. However, encryption does not prevent a volume from being moved or migrated - the provider's orchestration layer relocates encrypted volumes just as easily as unencrypted ones, so B is not a valid protection.