( ( A teacher ) ( ( should ( ( ( ( become ( familiar ( with ( ( the contents ) ( of ( the lessons ) ) ) ) ) ) ( within ( the unit ) ) ) and ) ( ( ( try ( the ( experiments themselves ) ) ) first ) ( before ( ( beginning ( the unit ) ) ( with ( the students ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN teacher)) (VP (MD should) (VP (VP (VB become) (ADJP (JJ familiar) (PP (IN with) (NP (NP (DT the) (NNS contents)) (PP (IN of) (NP (DT the) (NNS lessons)))))) (PP (IN within) (NP (DT the) (NN unit)))) (CC and) (VP (VB try) (NP (DT the) (NNS experiments) (PRP themselves)) (ADVP (RB first)) (PP (IN before) (S (VP (VBG beginning) (NP (DT the) (NN unit)) (PP (IN with) (NP (DT the) (NNS students))))))))) (. .)))
A teacher should become familiar with the contents of the lessons within the unit and try the experiments themselves first before beginning the unit with the students.
(ROOT (S (SBAR (IN If) (S (NP (DT an) (NN accident)) (VP (VBZ happens) (PP (IN during) (NP (DT a) (NN science) (NN experiment)))))) (, ,) (NP (NP (DT the) (JJ first) (NN thing)) (SBAR (S (NP (DT a) (NN student)) (VP (MD should) (VP (VB do)))))) (VP (VBZ is) (NP (NP (NN report)) (PP (TO to) (NP (DT the) (NN teacher))))) (. .)))