The rear wheels of an unloaded vehicle equipped with an automatic load-dependent braking force regulator (ALB) lock each time the brakes are strongly applied. What can be the cause?

You answered correctly by choosing both answer 1 (ALB is defect or wrongly adjusted) and answer 2 (Several spring leaves on the rear axle have broken).

The automatic load-dependent braking force regulator (ALB) ensures that the braking force for the rear axle adjusts according to the load. If the ALB is defective or incorrectly adjusted, it may apply too much braking force to the unloaded rear wheels, causing them to lock. Also, if several spring leaves on the rear axle are broken, the vehicle's suspension may not correctly indicate the load to the ALB, leading to similar problems.

Answer 3 (Strong fading of the brakes) is not correct for this situation because brake fading would lead to a loss of braking effect, not wheel locking. For similar questions, always focus on how automatic load-dependent regulators interact with vehicle load and the importance of suspension condition for correct brake functioning.