( ( ( ( ( ( Most snails ) ( are herbivores ) ) , ) but ) ( some ( are omnivores ) ) ) . )
(ROOT (S (S (NP (JJS Most) (NNS snails)) (VP (VBP are) (ADJP (JJ herbivores)))) (, ,) (CC but) (S (NP (DT some)) (VP (VBP are) (ADJP (JJ omnivores)))) (. .)))
Most snails are herbivores, but some are omnivores.
(ROOT (S (NP (NNS Mammals)) (VP (MD may) (RB either) (VP (VB be) (NP (NNS herbivores) (, ,) (NNS omnivores) (CC or) (NNS herbivores)))) (. .)))