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

You answered correctly. The signs warn drivers to expect a road used for winter sports activities, such as skiing, and to be prepared for packed snow or black ice on the road surface. This means you have to be extra careful and drive slowly, as both other people (skiers or winter sports participants) and slippery road conditions can be present. The warning sign with the skiing symbol indicates that these dangers are not limited just to sidewalks—they can be on the main road. That is why both answer 1 and answer 2 are correct.