Option A, which suggests using AWS Resource Access Manager from the management account to share the transit gateway with member accounts, is correct because AWS RAM allows the sharing of AWS resources with other AWS accounts within the same organization. Option C, which involves deploying an AWS CloudFormation stack set from the management account to automatically create a new VPC and a VPC transit gateway attachment in member accounts, and associating it with the transit gateway using its ID, is also correct. This approach ensures automation of the required resources each time a new member account is added, thereby meeting the company's need for efficiency and reducing operational effort.