( ( A ( 28-minute ( nuclear ( chain reaction ) ) ) ) ( ( was ( ( ( ( ( started , ) controlled ) , ) and ) stopped ) ) . ) )
(ROOT (S (NP (DT A) (JJ 28-minute) (JJ nuclear) (NN chain) (NN reaction)) (VP (VBD was) (VP (VP (VBN started)) (, ,) (VP (VBN controlled)) (, ,) (CC and) (VP (VBN stopped)))) (. .)))
A 28-minute nuclear chain reaction was started, controlled, and stopped.
(ROOT (S (NP (NNP Control) (NNS rods)) (VP (VBP play) (NP (NP (DT an) (JJ important) (NN role)) (PP (IN in) (NP (NP (DT the) (NN modulation)) (PP (IN of) (NP (DT the) (JJ nuclear) (NN chain) (NN reaction))))))) (. .)))