The actual total weight of a trailer pulled by a passenger car must not exceed:

The actual total mass of a trailer pulled by a passenger car must not exceed the actual total mass of that car - answer B. The unladen mass of the car (A) is a smaller value and is not the reference point here, and an increase of 40% (C) applies to lorries over 3.5 t, not a decrease.

The Road Traffic Act states that the actual total mass of a trailer pulled by a passenger car, a lorry with a maximum permissible mass of up to 3.5 t or a bus must not exceed the actual total mass of the towing vehicle, and that the actual total mass of a trailer pulled by a lorry over 3.5 t must not exceed the actual mass of that lorry increased by 40%. The actual total mass is the mass of the vehicle with its load and the people in it at a given moment. A trailer that is too heavy makes the combination sway and lengthens the braking distance, so before driving you also check the permitted towing mass entered in the car's vehicle registration certificate.

Legal basis: Art. 62 para. 1 point 1 and 2 and Art. 2 point 55 of the Road Traffic Act (Prawo o ruchu drogowym)