Answer: Cloud Monitoring

The correct answer is **Cloud Monitoring**. This GCP service is tailored for managing and analyzing time-series data, offering capabilities to collect, visualize, and alert on metrics and logs from your GCP resources and applications. It provides a comprehensive overview of your system's performance and availability, focusing on metrics like CPU utilization, latency, and error rates. - **Cloud Dataflow** is utilized for executing batch and streaming data processing pipelines. Although it can handle time-series data, it's not specialized for this purpose. - **Cloud Firestore** is a NoSQL document database that supports real-time synchronization and offline capabilities for mobile and web applications, not specifically for time-series data analysis. - **Cloud Spanner** is a globally distributed relational database service that can store time-series data but lacks the specialized features for its analysis that Cloud Monitoring provides. Thus, **Cloud Monitoring** stands out as the GCP service dedicated to managing and analyzing time-series data.

Author: LeetQuiz Editorial Team