Parents must ask questions like  
( Parents ( must ( ( ask questions ) like ) ) )
(ROOT (S (NP (NNS Parents)) (VP (MD must) (VP (VB ask) (NP (NNS questions)) (PP (IN like))))))
Parents should ask questions such as
( Parents ( should ( ( ask questions ) ( such as ) ) ) )
(ROOT (S (NP (NNS Parents)) (VP (MD should) (VP (VB ask) (NP (NNS questions)) (PP (JJ such) (PP (IN as)))))))