When it is helpful to activate the differential lock?

Your answer is correct because activating the differential lock is helpful in specific driving situations. According to German traffic rules, the differential lock should be used when individual drive wheels are spinning, such as when you are bogged down in mud or snow (option 1). It helps distribute power evenly to both wheels, improving traction. It is also useful when driving slowly straight ahead on slippery road surfaces (option 2), where maintaining grip is essential. However, it should not be used when maneuvering on dry road surfaces (option 3), as this can cause damage to the drivetrain and impair steering. Understanding when to use the differential lock helps maintain vehicle control and prevents mechanical issues.