( ( For humans ) ( , ( ( most ( skin cancers ) ) ( ( are ( ( associated ( with exposure ) ) ( to ( ultraviolet radiation ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (NNS humans))) (, ,) (NP (JJS most) (NN skin) (NNS cancers)) (VP (VBP are) (VP (VBN associated) (PP (IN with) (NP (NN exposure))) (PP (TO to) (NP (JJ ultraviolet) (NN radiation))))) (. .)))
For humans, most skin cancers are associated with exposure to ultraviolet radiation.
(ROOT (S (NP (NP (NNP Exposure)) (PP (TO to) (NP (JJ ultraviolet) (NN radiation)))) (VP (MD can) (VP (VP (VB increase) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN pigment)))) (PP (IN in) (NP (DT the) (NN skin)))) (CC and) (VP (VB make) (S (NP (PRP it)) (VP (VB appear) (NP (JJR darker))))))) (. .)))