They seem to think that he is descending.
( They ( ( seem ( to ( think ( that ( he ( is descending ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP seem) (S (VP (TO to) (VP (VB think) (SBAR (IN that) (S (NP (PRP he)) (VP (VBZ is) (VP (VBG descending))))))))) (. .)))
They think he is increasing the height.
( They ( ( think ( he ( is ( increasing ( the height ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP think) (SBAR (S (NP (PRP he)) (VP (VBZ is) (VP (VBG increasing) (NP (DT the) (NN height))))))) (. .)))