All three vehicles want to turn left. Which is in the correct lane?

Your answer is correct because the yellow car (vehicle 1) is in the correct lane to turn left.

In German traffic rules, when you want to turn left, you must be in the leftmost lane or, if multiple lanes are marked, in a lane designated for left turns. The yellow car is correctly positioned in the left lane before the intersection, making it ready and legally allowed to turn left.

The green car (vehicle 3) is in the middle lane, which is not appropriate for turning left unless it is clearly marked for that purpose, which it is not here. The truck (vehicle 2) is in the rightmost lane, which is generally meant for going straight or turning right, not left.

Therefore, only the yellow car is in the correct lane to make the left turn according to German road regulations. This ensures safe and predictable traffic flow.