Your client needs to analyze streaming data for real-time business intelligence. The solution should also integrate seamlessly with existing BigQuery datasets for combined analytics. Which GCP service will you recommend for streaming data?

The BigQuery Streaming API is the correct choice because it allows for real-time ingestion of data directly into BigQuery tables. This enables immediate analysis of streaming data alongside existing BigQuery datasets, fulfilling the client's requirement for real-time business intelligence and combined analytics. Cloud Pub/Sub is a messaging service, excellent for ingesting data streams but requires another service (like Dataflow) to load data into BigQuery for analysis. Dataflow is a fully managed service for executing Apache Beam pipelines, suitable for complex transformations and loading into BigQuery, but the Streaming API offers a more direct, real-time ingestion path for immediate analysis. Dataprep is for visual data preparation and exploration, not real-time streaming ingestion. Cloud Data Fusion is an ETL service for orchestrating data pipelines, not primarily for direct real-time streaming into BigQuery for immediate analytics.