Logic

I think we still need to emphasize on the difference between "factually incorrect" and "illogical". The students are being illogical to not derive that alligators would sprout flowers, given the premises they were presented with. Yes, it is incorrect to assume that alligator would somehow sprout flowers, but it was entirely logical to arrive at that assumption given the context they were in (just two premises). If the students wanted to counter the conclusion, they should have constructed another problem, such as:

- all green things sprout flowers
- alligators are green and thus sprout flowers
- alligators in fact do not sprout flowers
What conclusion can be drawn? Then you have a good argument that the all green things sprout flowers premise is wrong.