Why should you be ready to brake now?

Your answer is correct because in this situation, you must be prepared to brake since the driver of the brown vehicle might open their door or exit the vehicle unexpectedly. According to German traffic rules, when vehicles are parked on the roadside, it is important to anticipate that passengers or drivers could step out suddenly, which poses a hazard.

This rule is part of a general principle of caution in urban driving: always be ready to slow down or stop near parked cars, especially when doors might open or people might enter the road. This helps prevent accidents and ensures safety for all road users.

The other options, such as a pedestrian stepping onto the road or the bus moving across your lane, were less immediate or incorrect for this specific moment, because the priority caution was about the potential danger from the parked brown vehicle’s occupants.