( Water ( ( is ( ( the ( only ( common ( , ( safe substance ) ) ) ) ) ( that ( can ( ( exist ( in ( all ( three states ) ) ) ) ( at ( ( the ( same time ) ) ( on ( ( the surface ) ( of ( the Earth ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Water)) (VP (VBZ is) (NP (NP (DT the) (JJ only) (JJ common) (, ,) (JJ safe) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (VP (VB exist) (PP (IN in) (NP (DT all) (CD three) (NNS states))) (PP (IN at) (NP (NP (DT the) (JJ same) (NN time)) (PP (IN on) (NP (NP (DT the) (NN surface)) (PP (IN of) (NP (DT the) (NN Earth))))))))))))) (. .)))
Water is the only common, safe substance that can exist in all three states at the same time on the surface of the Earth.
(ROOT (S (NP (NNP Water)) (VP (VBZ exists) (PP (IN on) (NP (NP (NN earth)) (PP (IN in) (NP (NP (CD three) (NN matter) (NNS states)) (VP (VBZ states))))))) (. .)))