( ( Based ( upon ( ( the work ) ( done ( by ( ( many astronomers ) ( in ( ( the ( early part ) ) ( of ( the ( twentieth century ) ) ) ) ) ) ) ) ) ) ) ( , ( we ( now ( ( ( classify galaxies ) ( into ( ( ( ( ( ( ( ( three ( basic types ) ) , ) spiral ) , ) elliptical ) , ) and ) irregular ) ) ) . ) ) ) ) )
(ROOT (S (PP (VBN Based) (PP (IN upon) (NP (NP (DT the) (NN work)) (VP (VBN done) (PP (IN by) (NP (NP (JJ many) (NNS astronomers)) (PP (IN in) (NP (NP (DT the) (JJ early) (NN part)) (PP (IN of) (NP (DT the) (JJ twentieth) (NN century))))))))))) (, ,) (NP (PRP we)) (ADVP (RB now)) (VP (VB classify) (NP (NNS galaxies)) (PP (IN into) (NP (NP (CD three) (JJ basic) (NNS types)) (, ,) (NP (NN spiral)) (, ,) (NP (JJ elliptical)) (, ,) (CC and) (NP (NN irregular))))) (. .)))
Based upon the work done by many astronomers in the early part of the twentieth century, we now classify galaxies into three basic types, spiral, elliptical, and irregular .
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD three) (NNS types)) (PP (IN of) (NP (NNS galaxies))))) (. .)))