( ( The pupil ) ( ( controls ( ( ( the amount ) ( of light ) ) ( that ( enters ( the eye ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN pupil)) (VP (VBZ controls) (NP (NP (DT the) (NN amount)) (PP (IN of) (NP (NN light))) (SBAR (WHNP (WDT that)) (S (VP (VBZ enters) (NP (DT the) (NN eye))))))) (. .)))
The pupil controls the amount of light that enters the eye.
(ROOT (S (NP (NP (DT The) (NN pupil)) (PP (IN of) (NP (DT the) (NN eye)))) (VP (VBZ allows) (ADJP (JJ light) (S (VP (TO to) (VP (VB enter)))))) (. .)))
The pupil of the eye allows light to enter.