( ( The ( planet Mercury ) ) ( ( is ( ( the closest ) ( of ( ( the planets ) ( to ( the Sun ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN planet) (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (JJS closest)) (PP (IN of) (NP (NP (DT the) (NNS planets)) (PP (TO to) (NP (DT the) (NNP Sun))))))) (. .)))
The planet Mercury is the closest of the planets to the Sun.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (ADJP (ADJP (JJS closest)) (PP (TO to) (NP (DT the) (NN sun))))) (. .)))