Nested transactions allow performance tests to capture both individual and aggregated elements by grouping multiple related transactions and measuring their cumulative impact.
Option A (Aggregated metrics) provides summaries but lacks insight into individual elements.
Option B (Process optimization tracking) focuses on business process improvement, not test metrics.
Option C (Measuring underlying transactions) focuses only on individual transactions.

Mobile and browser-based applications often rely on APIs for data retrieval and processing. Unexpected API load can cause latency issues, bottlenecks, and system crashes.
Option A (Hard disk speed) is not a major issue in cloud-based or mobile systems.
Option B (Misconfigured host machine) affects on-premise systems, not mobile/browser-based applications.
Option D (Internet connectivity issues) is a user-side issue, not a system performance risk.