Logical fallacy?

Question

The following is an example of what type of fallacy:

All who truly studied received a good grade.
Since you did not receive a good grade, you did not truly study.

Answer 1

The conclusion supports its self: tautology, tautological fallacy. It may actually serve to exemplify many fallacies:

http://en.wikipedia.org/wiki/False_precision
http://en.wikipedia.org/wiki/Hasty_generalization
http://en.wikipedia.org/wiki/False_dilemma
http://en.wikipedia.org/wiki/Continuum_fallacy
http://en.wikipedia.org/wiki/Loki%27s_Wager
Where is the separation of good mark from bad, but that's a right/wrong judgment call, and no wrong need be done to get a bad mark, yet the 'not truly' part of the predicate seems to imply wrong doing as what is not true is false, what is not truly is falsely.

Answer 2

My logic is a bit rusty but I believe that would be an example of "post hoc, ergo propter hoc" or simply post hoc, for short.

One could also probably argue for petitio principii or "begging the question" as well since it makes the fallacious claim that the premise has only one result.
or A>B & B>A
it's basically a simple tautology

Answer 3

Isn't it how you study that counts ?

My brother failed all, but is one of the top tradespersons in our state. Proves the fallacy.

Answer 4

An "informal" fallacy . . ."hasty generalization".
http://en.wikipedia.org/wiki/Informal_fallacy