( ( This ( 11-year period ) ) ( ( is ( called ( the ( sunspot cycle ) ) ) ) . ) )
(ROOT (S (NP (DT This) (JJ 11-year) (NN period)) (VP (VBZ is) (VP (VBN called) (NP (DT the) (JJ sunspot) (NN cycle)))) (. .)))
This 11-year period is called the sunspot cycle.
(ROOT (S (NP (NNS Sunspots)) (VP (VBP occur) (PP (IN in) (NP (DT a) (CD 11) (NN year) (NN cycle)))) (. .)))