(S (S (BASENP (PRP They)) (VP (VP (VBD were) (PRN (COMMA ,) (ADVP (RB however)) (COMMA ,))) (VP (VBN hampered) (PP (IN by) (NP (NP (BASENP (NNS protesters)) (PP (IN on) (BASENP (DT the) (NN roof)))) (COMMA ,) (SBAR (WHNP (WP who)) (S (VP (PRN (COMMA ,) (PP (IN among) (BASENP (JJ other) (NNS things))) (COMMA ,)) (VP (VP (VBD threw) (BASENP (JJ caustic) (NN soda))) (PP (IN at) (BASENP (DT the) (NNS soldiers)))))))))))) (PERIOD .))