The tram has just become stationary at the stop. What is the right course of action?

Your answer is correct because when a tram has stopped at a stop, German traffic rules require that you neither endanger nor impede the tram. This means you must be cautious and give way to passengers boarding or leaving the tram, and avoid stopping or driving in a way that blocks the tram's movement or the passengers' access. Using the horn to warn the tram (option 3) is not appropriate here, as it does not improve safety or flow and could cause unnecessary disturbance. Remember, priority is given to the safety and smooth operation of public transport vehicles like trams.