There are lots of possibilities. Just choose a clause to be false, say the first one, and fill if the other variables arbitrarily.
The interpretation with a false, b and c true and all the other atoms true isn't a model of the knowledge base, as the first clause is false in this interpretation.
The interpretation with a false, b and c true and all the other atoms false isn't a model of the knowledge base, as the first (and seventh) clauses are false in this interpretation.