From which road sign onwards may you not exceed a permissible maximum speed of 60 km/h?

The first traffic sign (red circle with 60) is a speed limit sign according to German road rules. It means you must not drive faster than 60 km/h from where this sign is placed, until you encounter a sign that ends this limit. The second sign (white with crossed-out 60) means the 60 km/h speed limit ends. The third sign (blue with 60) is a minimum speed sign, indicating you must drive at least 60 km/h if conditions allow. Only the first sign sets up a maximum allowable speed of 60 km/h, which is what the question is about. That's why answer 1 is correct.