( ( ( ( ( ( A person ) ( can ( do ( without ( food ( for ( five ( weeks ( or more ) ) ) ) ) ) ) ) ) , ) but ) ( ( without water ) ( he ( can ( survive ( for ( ( only ( a few ) ) days ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT A) (NN person)) (VP (MD can) (VP (VB do) (PP (IN without) (NP (NP (NN food)) (PP (IN for) (NP (CD five) (NNS weeks) (QP (CC or) (JJR more))))))))) (, ,) (CC but) (S (PP (IN without) (NP (NN water))) (NP (PRP he)) (VP (MD can) (VP (VB survive) (PP (IN for) (NP (QP (RB only) (DT a) (JJ few)) (NNS days)))))) (. .)))
A person can do without food for five weeks or more, but without water he can survive for only a few days.
(ROOT (S (NP (JJS Most) (NNS people)) (VP (MD can) (VP (VB survive) (NP (QP (RB only) (DT a) (JJ few)) (NNS days)) (PP (IN without) (NP (NN water))))) (. .)))