( ( At ( ( the end ) ( of ( that time ) ) ) ) ( , ( they ( ( must ( repeat ( the cycle ) ) ) . ) ) ) )
(ROOT (S (PP (IN At) (NP (NP (DT the) (NN end)) (PP (IN of) (NP (DT that) (NN time))))) (, ,) (NP (PRP they)) (VP (MD must) (VP (VB repeat) (NP (DT the) (NN cycle)))) (. .)))
At the end of that time, they must repeat the cycle.
(ROOT (S (NP (DT The) (NN water) (NN cycle)) (VP (VBZ ends) (SBAR (IN with) (S (NP (PRP it)) (VP (VBZ repeats) (NP (PRP itself)))))) (. .)))
The water cycle ends with it repeats itself.