It's the first, because "Wurst" is male and singular
I said it in my head multiple times. they all work but D makes the most sense
1= wann der Zug ankommt.
2=wo der Schalter ist.
3=ob wir die Fahrkarten haben.
4=was wir zum Frühstück essen.
5=warum der Schaffner so laut schreit.
6= wie lange es noch dauert.
The other questions are not in German I hope I helped. I also speak German so it should be correct.