Why not F?

@Anevay, happy to help. F cannot be replaced by K because of our third rule, which says "If K is on a committee, J must also be on that committee," or K -> J. If we were to replace F with K, the planting committee would consist of K, H, L, M. This would violate Rule #3 because we have K on a committee without J. Does that make sense? Let us know if you have any other questions and best of luck with your studies!

Yes, thank you! I guess I was not applying the rules both ways and thought J could be on a committee without K.

@Anevay, I'm glad that makes more sense! Just to clarify, J can be on a committee without K (as is the case in the original trails committee we were given in this question). The rule "If K is on a committee, J must also be on that committee" is written as K -> J and the contrapositive is NOT J -> NOT K. Since J is never the Sufficient condition, it can exist on a committee without K. However, K cannot exist on a committee without J, which is why (A) is incorrect.