At what speed is a passenger car allowed to continue driving beyond these signs?

In the photo a narrow road enters a town; on the right there is sign D-42 "built-up area", and below it sign B-33 "speed limit" of 30 km/h. In a passenger car you may drive here at 30 km/h on the entire stretch of road running through the built-up area - answer C.

The Regulation on road signs and signals states that a prohibition sign placed below sign D-42 means that the prohibition applies up to sign D-43 or E-18a, except for the stretch of road where it has been changed or cancelled by another sign. So sign B-33 "30" below sign D-42 does not work like an ordinary limit, which is cancelled by sign B-34 or by a junction, but applies in the whole built-up area, up to the sign marking the end of the built-up area. Answer A talks about the limit being cancelled at the nearest junction - this is the rule for an ordinary B-33, not for one placed below D-42. Answer B refers to the board with the town name and a limit of 90 km/h - it confuses the built-up area with the town boundary and suggests that 90 is allowed in town. So you slow down to 30 km/h and drive like this through the whole village.

Legal basis: § 15 para. 4 and § 27 para. 1 of the Regulation on road signs and signals; Art. 20 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)