A company had a tight deadline to migrate its on-premises environment to AWS. It moved over Microsoft SQL Servers and Microsoft Windows Servers using the virtual machine import/export service and rebuild other applications native to the cloud. The team created both Amazon EC2 databases and used Amazon RDS. Each team in the company was responsible for migrating their applications, and they have created individual accounts for isolation of resources. The company did not have much time to consider costs, but now it would like suggestions on reducing its AWS spend.
Which steps should a Solutions Architect take to reduce costs?

A. Enable AWS Business Support and review AWS Trusted Advisor’s cost checks. Create Amazon EC2 Auto Scaling groups for applications that experience fluctuating demand. Save AWS Simple Monthly Calculator reports in Amazon S3 for trend analysis. Create a master account under Organizations and have teams join for consolidated billing.
B. Enable Cost Explorer and AWS Business Support. Reserve Amazon EC2 and Amazon RDS DB instances. Use Amazon CloudWatch and AWS Trusted Advisor for monitoring and to receive cost-savings suggestions. Create a master account under Organizations and have teams join for consolidated billing.
C. Create an AWS Lambda function that changes the instance size based on Amazon CloudWatch alarms. Reserve instances based on AWS Simple Monthly Calculator suggestions. Have an AWS Well-Architected framework review and apply recommendations. Create a master account under Organizations and have teams join for consolidated billing.
D. Create a budget and monitor for costs exceeding the budget. Create Amazon EC2 Auto Scaling groups for applications that experience fluctuating demand. Create an AWS Lambda function that changes instance sizes based on Amazon CloudWatch alarms. Have each team upload their bill to an Amazon S3 bucket for analysis of team spending. Use Spot Instances on nightly batch processing jobs.