A company is using AWS Organizations to implement a multi-account strategy.

The correct answer is C. Use AWS Resource Access Manager (AWS RAM) to share Account-A’s VPC subnets with the remaining member accounts. Configure the member accounts to use the shared subnets to launch workloads.

This answer is correct because AWS RAM is a service that helps you securely share your AWS resources across AWS accounts, within your organization or organizational units (OUs), and with IAM roles and users for supported resource types1.One of the supported resource types is VPC subnets2, which means you can share the subnets in Account-A’s VPC with the other member accounts using AWS RAM. This way, you can meet the requirements of using a centrally managed VPC, avoiding duplicate VPCs in each account, and launching workloads in shared subnets.You can also control the access to the shared subnets by using IAM policies and resource-based policies3, which can prevent one account from modifying another account’s resources.

The other options are incorrect because:

A.Using aCloudFormation template in the member accounts to launch workloads and using the Fn::ImportValue function to obtain the subnet ID values is not a solution, because Fn::ImportValue can only import values that have been exported by another stack within the same region4. This means that you cannot use Fn::ImportValue to reference the subnet IDs that are exported by Account-A’s CloudFormation template, unless all the member accounts are in the same region as Account-A. This option also does not avoid creating duplicate VPCs in each account, which is one of the requirements.

B. Using a transit gateway in the VPC within Account-A and configuring the member accounts to use the transit gateway to access the subnets in Account-A to launch workloads is not a solution, because a transit gateway does not allow you to launch workloads in another account’s subnets.A transit gateway is a network transit hub that enables you to route traffic between your VPCs and on-premises networks5, but it does not enable you to share subnets across accounts.

D. Creating a peering connection between Account-A and the remaining member accounts and configuring the member accounts to use the subnets in Account-A through the VPC peering connection to launch workloads is not a solution, because a VPC peering connection does not allow you to launch workloads in another account’s subnets.A VPC peering connection is a networking connection betweentwo VPCs that enables you to route traffic between them privately6, but it does not enable you to share subnets across accounts.