( ( ( ( ( ( In '93 ) ( he ( climbed ( ( ( K2 ( -LRB- ( ( 8,680 meters ) -RRB- ) ) ) , ) ( ( the ( second-highest mountain ) ) ( in ( the world ) ) ) ) ) ) ) , ) and ) ( ( what ( people think ) ) ( is ( the ( ( most dangerous ) summit ) ) ) ) ) . )
(ROOT (S (S (PP (IN In) (NP (CD '93))) (NP (PRP he)) (VP (VBD climbed) (NP (NP (NP (NNP K2)) (PRN (-LRB- -LRB-) (NP (CD 8,680) (NNS meters)) (-RRB- -RRB-))) (, ,) (NP (NP (DT the) (JJ second-highest) (NN mountain)) (PP (IN in) (NP (DT the) (NN world))))))) (, ,) (CC and) (S (SBAR (WHNP (WP what)) (S (NP (NNS people)) (VP (VBP think)))) (VP (VBZ is) (NP (DT the) (ADJP (RBS most) (JJ dangerous)) (NN summit)))) (. .)))
In '93 he climbed K2 (8,680 meters), the second-highest mountain in the world, and what people think is the most dangerous summit.
(ROOT (S (NP (NNP K2)) (VP (VBZ is) (NP (NP (DT the) (JJ second) (JJS highest) (NN mountain)) (PP (IN in) (NP (DT the) (NN world)))) (, ,) (PP (IN at) (NP (IN over) (CD 28,000) (NNS feet)))) (. .)))