Option A is the correct choice for implementing a data lake solution. Amazon S3 is a highly scalable and durable object storage service that can store large volumes of structured and unstructured data. It can handle various data formats and is cost-effective for long-term storage. Amazon EMR is a powerful data processing and analysis service that can process and analyze data stored in S3 using frameworks like Apache Spark, Hadoop, or PrestoSQL. This combination of services provides a flexible and scalable solution for data lake storage and processing. Option B is not suitable for unstructured data, as RDS is designed for relational databases. Option C is a good choice for data warehousing but may not be as flexible for unstructured data. Option D is useful for real-time data processing but may not be as cost-effective for large volumes of data storage.