( ( The ( boiling point ) ) ( ( becomes ( lower ( as ( ( the ( external pressure ) ) ( is reduced ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ boiling) (NN point)) (VP (VBZ becomes) (ADVP (ADVP (RBR lower)) (SBAR (IN as) (S (NP (DT the) (JJ external) (NN pressure)) (VP (VBZ is) (VP (VBN reduced))))))) (. .)))
The boiling point becomes lower as the external pressure is reduced.
(ROOT (S (NP (NNP External) (NN pressure)) (VP (VBZ affects) (NP (NP (DT the) (JJ boiling) (NN point)) (PP (IN of) (NP (NN water))))) (. .)))