What must you be prepared for when you pass these traffic signs?

Your answer is correct. The warning sign with an exclamation mark combined with the additional panel showing a skier indicates a special caution related to winter sports.

According to German traffic rules, when you see this combination, you must be prepared for the possibility that the road may be used for winter sports activities, such as skiing or sledding. This means there could be people crossing the road or using the area nearby for winter sports, so you need to drive carefully.

Additionally, the sign warns that there may be packed snow or black ice on the roadway, which makes the road slippery and requires more cautious driving.

The third option, that only the pavements are used for winter sports, is incorrect because the warning applies directly to the road conditions and use, not just sidewalks.

So, the important points to remember are:

- The road may be used for winter sports, so expect skiers or winter sport users.
- The road surface may be hazardous with packed snow or black ice.
- Extra caution and reduced speed are necessary to ensure safety in these conditions.