Why do you have to wait before the left turn?

You have to wait because when you turn left, you must let oncoming traffic go first, and that includes oncoming motorcycles. In German rules, a motorcycle is treated like any other vehicle in the opposite direction: if it is coming toward you on the road you’re leaving, it has priority to continue straight (or to turn right from its perspective) while you are crossing its path.

That’s why answer 1 (motorbike) is correct: a motorcycle can be harder to notice and can be faster than it looks, so you only turn when you are sure the gap is large enough and you won’t force it to brake.

Why not the others in this situation: a car or bicycle would only be a reason to wait if they are actually oncoming in the lane you must cross, or if a bicycle is going straight in the same direction on your right (typical “right-side cyclist” conflict when turning). Since the correct solution names only the motorbike, the key rule being tested is “left turn yields to oncoming traffic,” with the motorbike as the specific hazard.

Rule of thumb for similar questions: turning left almost always means “yield to oncoming traffic” first; scan specifically for motorcycles because they’re easy to miss, then turn only when you can do it without anyone else having to react.