( This ( ( is ( why ( ( a ( human being ) ) ( can ( ( ( survive ( no longer ) ) ( than ( few days ) ) ) ( without water ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (SBAR (WHADVP (WRB why)) (S (NP (DT a) (JJ human) (NN being)) (VP (MD can) (VP (VB survive) (ADVP (RB no) (RB longer)) (PP (IN than) (NP (JJ few) (NNS days))) (PP (IN without) (NP (NN water)))))))) (. .)))
This is why a human being can survive no longer than few days without water.
(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))))) (. .)))