An emergency shutdown could be activated in which two ways?

An emergency shutdown can indeed be activated in two principal ways: automatically or manually. An automatic shutdown typically occurs when a system detects a critical failure or anomaly, prompting the system to initiate the shutdown process without human intervention to prevent further hazards. This can include scenarios like temperature exceeding a safe limit or the failure of critical components.

On the other hand, a manual shutdown requires an operator to take action to initiate the shutdown. This is often necessary in situations where a potential hazard is recognized before an automatic system can respond or in response to a specific operational decision.

The other options do not accurately represent the established methods for emergency shutdown protocols in power engineering contexts. The terms silently or loudly, quickly or slowly, and online or offline do not align with how emergency shutdowns are structured in practice, as these choices do not address the methodologies of activation but rather describe unrelated characteristics or dynamics of emergency response systems.