A solutions architect is designing a highly available Amazon ElastiCache for Redis based solution.

This answer is correct because it provides high availability at the node level and at the Region level for the ElastiCache for Redis solution. A Multi-AZ Redis replication groupconsists of a primary cluster and up to five read replica clusters, each in a different Availability Zone. If the primary cluster fails, one of the read replicas is automatically promoted to be the new primary cluster. A Redis replication group with shards enables partitioning of the data across multiple nodes, which increases the scalability and performance of the solution. Each shard can have one or more replicas to provide redundancy and read scaling.