( Comets ( ( ( grow ( tails ( of ( ( gas and ) dust ) ) ) ) ( as ( they ( near ( the sun ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Comets)) (VP (VBP grow) (NP (NP (NNS tails)) (PP (IN of) (NP (NN gas) (CC and) (NN dust)))) (PP (IN as) (NP (NP (PRP they)) (PP (IN near) (NP (DT the) (NN sun)))))) (. .)))
Comets grow tails of gas and dust as they near the sun.
(ROOT (S (NP (JJ Comet) (NNS tails)) (VP (ADVP (RB always)) (VBP point) (PRT (RP away)) (PP (IN from) (NP (NP (DT the) (NN sun)) (PP (RB instead) (IN of) (S (VP (VBG trailing) (PP (IN behind) (NP (DT the) (ADJP (JJ comet) (PP (IN because) (NP (NN dust) (NNS particles)))) (NN recoil))))))))) (. .)))