( ( An ( Earth year ) ) ( ( is ( ( how long ) ( Earth ( takes ( to ( orbit ( the sun ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NNP Earth) (NN year)) (VP (VBZ is) (SBAR (WHADVP (WRB how) (RB long)) (S (NP (NNP Earth)) (VP (VBZ takes) (S (VP (TO to) (VP (VB orbit) (NP (DT the) (NN sun))))))))) (. .)))
An Earth year is how long Earth takes to orbit the sun.
(ROOT (S (NP (PRP It)) (VP (VBZ takes) (PP (IN about) (NP (NP (CD one) (NN year)) (PP (IN for) (NP (NN earth))))) (S (VP (TO to) (VP (VB orbit) (NP (DT the) (NN sun)))))) (. .)))
It takes about one year for earth to orbit the sun.