(S (S (PP (IN Due) (PP (TO to) (NP (BASENP (DT the) (NN planet) (POS 's)) (NN size)))) (COMMA ,) (S (NP (BASENP (JJ current) (NNS theories)) (PP (IN about) (BASENP (JJ superheated) (JJ giant) (NNS planets)))) (VP (VBP find) (S (S (BASENP (PRP it)) (ADJP (JJ hard))) (S (VP (TO to) (VP (VB explain) (SBAR (WHADVP (WRB why)) (S (BASENP (PRP it)) (VP (VBZ is) (ADJP (RB so) (JJ large)))))))))))) (PERIOD .))