For 12a, they are asking about winter sports, they could ask about all sports.
For 12b, they ask an audience about the show they came to see; which is inherently a bias as they are going to be partial towards certain contestants; they could ask them about random contestants of unaffiliated shows.
For 13a, it should be continuous, and I'm sorry but I don't know the types of graphs available.
For 13b, I believe it should be discreet, and once again apologize for not knowing the types of graphs.