The question revolves around adding more IP address space to an existing VPC with the least operational overhead. The VPC is already assigned the 10.10.0.0/16 CIDR block, which means it has a large range of IP addresses available. The specific Availability Zone in question has run out of space in its 10.10.1.0/24 CIDR block, but there is available capacity in the broader 10.10.1.0/22 CIDR block within the VPC. Option A suggests updating the AWS::EC2::Subnet resource for the Availability Zone in the CloudFormation stack to change the CidrBlock property to 10.10.1.0/22. This approach directly addresses the issue by expanding the subnet's IP address range within the existing VPC, leveraging the available capacity without the need for creating new resources or modifying the VPC's overall CIDR block. This method incurs the least operational overhead as it involves a straightforward update to an existing resource in the CloudFormation stack. Options B and C involve unnecessary changes to the VPC's CIDR block or creating a new stack, which are more complex and not required to solve the immediate problem. Option D suggests creating a new subnet, which, while feasible, does not utilize the available capacity in the existing subnet's broader CIDR block and thus is not the most efficient solution.