@MonicaAponte to build onto your comment - I think it isn't outside knowledge because the argument is 'telling us' that tigers are mammals.. Which is to say, it is expected of us to assume that tigers are mammals as a result of the presented premise and conclusion.

@DeJCastro This is my type of studying - I always try to make funny or memorable examples. Throw back to an intro psych course where a prof use the example "Everytime so and so masterbated they first turned on their bedside lamp. Now everytime they turn the lamp on they get aroused."