This solution provides the most effective and standard AWS-native approach for the stated requirements. DynamoDB global tables create a multi-active database, allowing the secondary region's table to be fully writable and independent immediately. For RDS for MySQL, a cross-region read replica is the standard disaster recovery pattern. During a disaster, the read replica can be promoted to a standalone, writable DB instance, which severs its replication link to the primary and allows it to function independently. This combination fully addresses the disaster recovery scenario for both services.

B. DynamoDB Accelerator (DAX) is an in-memory cache for DynamoDB, not a cross-region data replication or disaster recovery mechanism.
C. RDS Multi-AZ provides high availability within a single AWS Region by creating a standby in a different Availability Zone. It cannot be used for cross-region disaster recovery.
D. Using DynamoDB Streams and AWS Lambda is a custom, manual approach to replicate data. DynamoDB global tables are the fully managed, purpose-built, and recommended service for this use case.

1. AWS DynamoDB Developer Guide, "Global tables": "Global tables build on the global Amazon DynamoDB footprint to provide you with a fully managed, multi-region, and multi-active database that delivers fast, local, read and write performance for massively scaled, global applications." This supports the use of global tables for an independent, writable copy in the secondary region.

2. AWS RDS User Guide, "Working with read replicas" -> "Promoting a read replica to be a standalone DB instance": "You can promote a read replica into a standalone DB instance. When you promote a read replica, the DB instance is rebooted before it becomes available... This is useful for implementing disaster recovery." This confirms the process for making the RDS instance independent.

3. AWS RDS User Guide, "High availability (Multi-AZ) for Amazon RDS": "RDS Multi-AZ deployments provide enhanced availability and durability for RDS DB instances, making them a natural fit for production database workloads. When you provision a Multi-AZ DB instance, RDS automatically creates a primary DB instance and synchronously replicates the data to a standby instance in a different Availability Zone (AZ)." This confirms Multi-AZ is a single-region, intra-AZ solution.

4. AWS DynamoDB Developer Guide, "In-Memory Acceleration with DynamoDB Accelerator (DAX)": "DynamoDB Accelerator (DAX) is a fully managed, highly available, in-memory cache for Amazon DynamoDB... DAX is not suitable for applications that require eventually consistent reads or that perform write-intensive operations." This clarifies that DAX is a cache, not a replication tool.