OpenTelemetry is a CNCF project providing standardized APIs and SDKs for collecting observability data. Among its supported telemetry signals are metrics, logs, and traces. Option C is correct because traces are a core OpenTelemetry signal type that captures the journey of requests across distributed systems, making them vital for detecting latency, dependencies, and bottlenecks.

Option A (user interface), Option B (networking), and Option D (databases) represent system components or domains, not observability signals. While OpenTelemetry can instrument applications in these areas, it expresses data through its standard telemetry signals.

By supporting consistent collection of logs, metrics, and traces, OpenTelemetry enables observability pipelines to integrate seamlessly with different backends while avoiding vendor lock-in. Traces specifically provide visibility into distributed microservices, which is critical in cloud native environments.

--- CNCF Observability Whitepaper

--- OpenTelemetry CNCF Project Documentation

--- Cloud Native Platform Engineering Study Guide