All knowleges is good $\equiv \forall ( knowledge \rightarrow Good)$Contrapositive of it $\forall ( BAD \rightarrow Not(knowledge))$
All knowleges is Difficult $\equiv \forall ( knowledge \rightarrow difficult)$ contrapositive of it $\equiv \forall ( Easy \rightarrow Not(knowledge))$
D is answer . for implication Contrapositive is true always