( ( Cesium ( , ( gallium ( , ( and mercury ) ) ) ) ) ( ( are ( ( the ( only ( three metals ) ) ) ( that ( are ( liquid ( at ( room temperature ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Cesium) (, ,) (NNP gallium) (, ,) (CC and) (NNP mercury)) (VP (VBP are) (NP (NP (DT the) (JJ only) (CD three) (NNS metals)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (ADJP (JJ liquid) (PP (IN at) (NP (NN room) (NN temperature))))))))) (. .)))
Cesium, gallium , and mercury are the only three  metals that are liquid at room temperature.
(ROOT (S (NP (NNP Mercury)) (VP (VBZ is) (RB not) (NP (DT a) (JJ solid) (ADJP (RB even) (PP (IN at) (NP (NN room)))) (NN temperature))) (. .)))