Which of the following is the best description of the relationship between a cause and a trigger for slope failure?
1) A cause is the event or action that directly leads to slope failure, while a trigger is a factor that initiates the failure process.
2) A cause and a trigger are the same thing and can be used interchangeably in the context of slope failure.
3) A cause is a natural factor that leads to slope failure, while a trigger is a human-induced factor.
4) A cause is the initial condition that sets the stage for slope failure, while a trigger is the final event that causes the failure.