( ( Most ( of ( ( the water ) ( in ( ( Earth 's ) oceans ) ) ) ) ) ( ( may ( have ( come ( from comets ) ) ) ) . ) )
(ROOT (S (NP (NP (JJS Most)) (PP (IN of) (NP (NP (DT the) (NN water)) (PP (IN in) (NP (NP (NNP Earth) (POS 's)) (NNS oceans)))))) (VP (MD may) (VP (VB have) (VP (VBN come) (PP (IN from) (NP (NNS comets)))))) (. .)))
Most of the water in Earth's oceans may have come from comets.
(ROOT (S (NP (NP (JJS Most)) (PP (IN of) (NP (NP (NN earth) (POS 's)) (NN water)))) (VP (VBZ is) (VP (VBN located) (PP (IN in) (NP (NNS oceans)))))))