( Things ( ( can ( happen ( that ( can ( destroy ( a relationship ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Things)) (VP (MD can) (VP (VB happen) (SBAR (IN that) (S (VP (MD can) (VP (VB destroy) (NP (DT a) (NN relationship)))))))) (. .)))
Things can happen that can destroy a relationship.
(ROOT (S (NP (NNP Energy) (PRP it)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN destroyed)))) (. .)))