( ( Nuclear fusion ) ( ( occurs ( which ( ( causes ( the star ) ) ( to glow ) ) ) ) . ) )
(ROOT (S (NP (JJ Nuclear) (NN fusion)) (VP (VBZ occurs) (SBAR (WHNP (WDT which)) (S (VP (VBZ causes) (NP (DT the) (NN star)) (PP (TO to) (NP (NNP glow))))))) (. .)))
Nuclear fusion occurs which causes the star to glow.
(ROOT (S (NP (NP (JJ Nuclear) (NN fusion)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ results) (PP (RB because) (IN of) (NP (NP (JJ great) (NN pressure)) (PP (IN at) (NP (NP (DT the) (NN center)) (PP (IN of) (NP (DT a) (NN star)))))))))) (, ,)) (VP (VBZ causes) (S (NP (NNS stars)) (VP (TO to) (VP (VB shine))))) (. .)))