正解:C
The Salesforce Trust site is where an org's service status and performance degradation information can be found. The Salesforce Trust site is a resource that provides transparency and real-time information about the availability, performance, security, privacy, and compliance of the Salesforce platform. The Salesforce Trust site allows the user to check the current and historical status of their org's instance, as well as subscribe to notifications and alerts about any maintenance or incidents. The AppExchange portal is a resource that provides access to thousands of apps and components that extend the functionality and features of the Salesforce platform. The AppExchange portal does not provide information about the service status and performance of the Salesforce platform. Salesforce Help is a resource that provides documentation, guides, videos, and support for Salesforce users who need assistance with using or troubleshooting Salesforce products and features. Salesforce Help does not provide information about the service status and performance of the Salesforce platform.