To maximize read performance for a Cloud SQL instance that needs to handle around 25,000 read IOPS, it's crucial to select a machine type and configuration that can support such a high IOPS requirement. Option C is the correct choice because it provides a High Memory machine type with 16 vCPUs, 104 GB of RAM, and a large 4 TB SSD. The large SSD is particularly important as it can support the high read IOPS requirement. The High Memory machine type is suitable for memory-intensive applications, and the 16 vCPUs ensure that the instance can handle the workload efficiently. The other options either do not provide enough storage to support the required IOPS (A and B) or are unnecessarily expensive due to the Enterprise edition (D) without providing additional benefits for the read IOPS requirement.