The correct option is Read replicas.

Read replicas create one or more readable secondary databases that can serve read only queries so you can divert a portion of the read workload away from the primary database. This reduces latency and increases read throughput by distributing queries across the replicas rather than overloading the primary.

Read replicas are designed for read scale out and allow multiple replicas to handle read traffic while the primary focuses on writes, which directly addresses the scenario of a sudden increase in read requests.

The Columnstore indexes option is incorrect because columnstore indexes are an index structure that improves analytical query performance and storage compression on a single database. They do not create additional database instances or readable secondaries to offload read traffic.

The Elastic pools option is incorrect because elastic pools let multiple databases share resources to optimize cost and manage variable load. They do not provide replicas or a mechanism to distribute read queries across separate database instances.

The Active geo replication option is incorrect in this scenario because active geo replication is focused on business continuity and cross region failover and it creates readable secondaries primarily for disaster recovery. While those secondaries can be used for reads they are not intended as the primary mechanism for local read scale out and they can introduce higher replication lag and cross region latency.

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