Which solution will meet these requirements?

Explanations:

Amazon CloudFront is a content delivery network (CDN) that caches static content closer to users but does not provide a dedicated caching layer for dynamic database queries. It does not encrypt cache data or provide a caching solution directly in front of a database like RDS.

Amazon ElastiCache for Memcached is a caching solution that supports in-memory data storage and retrieval, but it does not support encryption at rest or in transit by default. Additionally, it is less suitable for scenarios requiring high availability compared to Redis.

Amazon ElastiCache for Redis in cluster mode provides a managed caching layer with support for encryption in transit and at rest. It offers high availability through Redis replication and cluster configuration, making it ideal for caching database queries while meeting the encryption and availability requirements.

Amazon DynamoDB Accelerator (DAX) is designed specifically for DynamoDB and is not applicable for use with Amazon RDS. While DAX provides in-memory caching with encryption options, it does not fulfill the requirement of caching in front of an RDS database.