The correct answer is 'Synthetic transaction monitoring' because it involves simulating user interactions with a web application to test its availability and performance. By running predefined scripts, a cloud administrator can ensure that the application is not just available but also functioning as expected. On the other hand, 'Resource utilization monitoring' focuses on the consumption of computing resources rather than availability, 'Network performance monitoring' is focused on the network health and may not account for the state of the application itself, and 'Agent-based monitoring' can monitor a wide array of metrics but isn't specifically designed to test application workflow as would be desired for SLA uptime verification.