Answer - C.
As Database servers contain confidential information, so for a security perspective, it should be deployed in a Private Subnet.
Amazon Virtual Private Cloud (Amazon VPC) enables the user to launch AWS resources into a virtual network that a user has defined.
Option A is incorrect because NAT devices (NAT Gateway, Nat Instance) allow instances in private subnets to connect to the internet, other VPCs, or on-premises networks.
It is deployed in a public subnet.
Option B is incorrect because bastion host is a server whose purpose is to provide access (SSH access) to a private network from an external network, such as the Internet.
It is deployed in a public subnet.
Option D is incorrect because an Internet Gateway is a horizontally scaled, redundant, and highly available VPC component that allows communication between your VPC and the internet.
