( Mercury ( ( is ( ( the ( only ( metallic element ) ) ) ( that ( is ( a ( ( liquid ( at room ) ) temperature ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (NP (NP (DT the) (RB only) (JJ metallic) (NN element)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (NP (DT a) (ADJP (JJ liquid) (PP (IN at) (NP (NN room)))) (NN temperature))))))) (. .)))
Mercury is the only metallic element that is a 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)))))))) (. .)))