I hit these "tough" questions with no issue but then when he says this an "easy" question I always get them wrong

I feel that the strength of an argument depends on the ability to eliminate outside viewpoints. Where the Disney argument, the premises eliminate other possible conclusions. The tiger argument goes the same way by giving an example of a dangerous mammal who shouldn't have a pet.

The trash can question although gives reason to believe the conclusion, it does not create the elimination of any other possible conclusions.