What should you anticipate in this situation?

You are correct in choosing answer 1: "pull out and cross the centre of the road." In situations where a vehicle in front, such as a bus at a bus stop, signals and begins to pull out, German traffic law (§ 20 StVO) requires you to anticipate that the bus will rejoin traffic and may need to move into your lane. This means you should expect to adjust your position, possibly pulling out and crossing the center of the road if it is safe and allowed, to give the bus space. You must not simply overtake without considering the bus’s right to merge, and you must not brake and block the center unnecessarily if it is your responsibility to facilitate safe merging. Always anticipate the movements of public transport vehicles at marked stops and be prepared to yield if necessary. This helps to prevent dangerous situations and ensures the safety of passengers and other road users.