K is an apple.
All fruits with the color red contain a large amount of vitamin C. All apples are fruits with the color red. All fruits containing a large amount of vitamin C are beneficial to people.  No fruits that are beneficial to people are on a warning list. If K is not beneficial to people and also not an apple, then it is a fruit with the color red.
∀x (RedFruit(x) → VC(x)) ∀x (Apple(x) → RedFruit(x)) ∀x (VC(x) → Benefit(x)) ∀x (Benefit(x) → ¬WarningList(x)) ¬(Benefit(k) ∧ Apple(k)) → RedFruit(k)