Which of the following vehicles can you overtake if you ride a motorcycle on the road, once you go past this sign?

In the photo you are riding on a two-way roadway with a double solid line, and on the right there is sign B-25 "no overtaking". Beyond this sign, when riding a motorcycle, you may overtake only a single-track motorcycle - answer B.

The Regulation on road signs and signals states that sign B-25 prohibits drivers of power-driven vehicles from overtaking multi-track power-driven vehicles. So you check each answer: an agricultural tractor without a trailer is a power-driven vehicle on four wheels - multi-track, so the ban applies; a light quadricycle (a small vehicle with four wheels, up to 45 km/h) is also a multi-track power-driven vehicle - the ban applies; a single-track motorcycle leaves one track, so B-25 does not protect it and you may overtake it. However, the sign does not free you from the general rules of overtaking: you must be sure that there is enough space and visibility, keep a lateral clearance of at least 1 m from the motorcycle you are overtaking, and in the photo you must not cross the double solid line while doing this - the overtaking must fit within your half of the roadway.

Legal basis: § 23 para. 1 of the Regulation on road signs and signals; Art. 24 para. 1 and 2 and Art. 2 point 42c of the Road Traffic Act (Prawo o ruchu drogowym)