( ( As ( altitude increases ) ) ( , ( ( the density ) ( ( decreases ( with ( a ( decreasing rate ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN As) (NP (NN altitude) (NNS increases))) (, ,) (NP (DT the) (NN density)) (VP (VBZ decreases) (PP (IN with) (NP (DT a) (VBG decreasing) (NN rate)))) (. .)))
As altitude increases, the density decreases with a decreasing rate.
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN altitude)) (VP (VBZ decreases)))) (, ,) (NP (NP (DT the) (NN density)) (PP (IN of) (NP (NN air)))) (VP (VBZ decreases)) (. .)))