Which of the following is a Server side trigger in SuiteFlow?

Before load is a server-side trigger in SuiteFlow that is executed during the record's lifecycle before the data is loaded into the user interface. This trigger allows for actions to be performed just before the record is displayed to the user, providing an opportunity to modify, validate, or enhance data as needed before it is presented.

In the context of SuiteFlow, server-side triggers are designed to respond to backend events that occur within the system. The before load trigger can be utilized to enforce data integrity or implement business rules that must be satisfied prior to the record being presented, making it a crucial point in process automation.

Other triggers, while important, function under different circumstances or at different times in the transaction process, and therefore, do not qualify as server-side triggers within the SuiteFlow framework.