( ( Sulfur ( ( dioxide and ) trioxide ) ) ( ( are ( highly toxic ) ) . ) )
(ROOT (S (NP (NNP Sulfur) (NN dioxide) (CC and) (NN trioxide)) (VP (VBP are) (ADJP (RB highly) (JJ toxic))) (. .)))
Sulfur dioxide and trioxide are highly toxic.
(ROOT (S (NP (NNP Sulfur)) (VP (MD can) (VP (VB combine) (PP (IN with) (NP (NN oxygen))) (S (VP (TO to) (VP (VB produce) (NP (NN sulfur) (NN trioxide))))))) (. .)))