Oracle Cloud Infrastructure Key Management is a managed service that enables you to encrypt your data using keys that you control.

DATA ENCRYPTION
Protect customer data at-rest and in-transit in a way that allows customers to meet their security and compliance requirements for cryptographic algorithms and key management The Oracle Cloud Infrastructure Block Volume service always encrypts all block volumes, boot volumes, and volume backups at rest by using the Advanced Encryption Standard (AES) algorithm with 256-bit encryption. By default all volumes and their backups are encrypted using the Oracle-provided encryption keys. Each time a volume is cloned or restored from a backup the volume is assigned a new unique encryption key.
The File Storage service encrypts all file system and snapshot data at rest. By default all file systems are encrypted using Oracle-managed encryption keys. You have the option to encrypt all of your file systems using the keys that you own and manage using the Vault service.
Object Storage employs 256-bit Advanced Encryption Standard (AES-256) to encrypt object data on the server. Each object is encrypted with its own data encryption key. Data encryption keys are always encrypted with a master encryption key that is assigned to the bucket. Encryption is enabled by default and cannot be turned off. By default, Oracle manages the master encryption key.
Reference:
https://docs.cloud.oracle.com/en-us/iaas/Content/Block/Concepts/overview.htm
https://docs.cloud.oracle.com/en-us/iaas/Content/Object/Concepts/objectstorageoverview.htm
https://docs.cloud.oracle.com/en-us/iaas/Content/File/Concepts/filestorageoverview.htm Oracle Cloud Infrastructure Key Management is a managed service that enables you to encrypt your data using keys that you control.
IAM, Autoscaling and functions cannot be used with Key Management and hence are incorrect options.

https://docs.oracle.com/en/solutions/deploy-ebusiness-suite-oci/index.html#GUID-0CA881FD-D96F-4885-BC77-62E3A66EFF95

When you work with Oracle Cloud Infrastructure, one of the first steps is to set up a virtual cloud network (VCN) for your cloud resources.
VIRTUAL CLOUD NETWORK (VCN) :
A virtual, private network that you set up in Oracle data centers. It closely resembles a traditional network, with firewall rules and specific types of communication gateways that you can choose to use. A VCN resides in a single Oracle Cloud Infrastructure region and covers a single, contiguous IPv4 CIDR block of your choice. See Allowed VCN Size and Address Ranges. The terms virtual cloud network, VCN, and cloud network are used interchangeably in this documentation. For more information, see VCNs and Subnets.
SUBNETS :
Subdivisions you define in a VCN (for example, 10.0.0.0/24 and 10.0.1.0/24). Subnets contain virtual network interface cards (VNICs), which attach to instances. Each subnet consists of a contiguous range of IP addresses that do not overlap with other subnets in the VCN. You can designate a subnet to exist either in a single availability domainavailability domain or across an entire region (regional subnets are recommended). Subnets act as a unit of configuration within the VCN: All VNICs in a given subnet use the same route table, security lists, and DHCP options (see the definitions that follow). You can designate a subnet as either public or private when you create it. Private means VNICs in the subnet can't have public IP addresses. Public means VNICs in the subnet can have public IP addresses at your discretion. See Access to the Internet.