( Mercury ( ( is ( unique ( in ( being ( ( the ( only ( metallic element ) ) ) ( that ( is ( liquid ( at ( room temperature ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (ADJP (JJ unique) (PP (IN in) (S (VP (VBG being) (NP (NP (DT the) (RB only) (JJ metallic) (NN element)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ liquid) (PP (IN at) (NP (NN room) (NN temperature))))))))))))) (. .)))
Mercury is unique in being the only metallic element that is liquid at room temperature.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (CD one) (NN metal)) (SBAR (WHNP (WDT that)) (S (VP (VBZ melts) (PP (IN below) (NP (NN room) (NN temperature)))))))) (. .)))