Many business firms have  casual days  for office attire.
( ( Many ( business firms ) ) ( ( have ( ( casual days ) ( for ( office attire ) ) ) ) . ) )
(ROOT (S (NP (JJ Many) (NN business) (NNS firms)) (VP (VBP have) (NP (NP (JJ casual) (NNS days)) (PP (IN for) (NP (NN office) (NN attire))))) (. .)))
There would be a strike if business firms didn't practice casual days.
( There ( ( would ( ( be ( a strike ) ) ( if ( ( business firms ) ( ( did n't ) ( practice ( casual days ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (MD would) (VP (VB be) (NP (DT a) (NN strike)) (SBAR (IN if) (S (NP (NN business) (NNS firms)) (VP (VBD did) (RB n't) (VP (VB practice) (NP (JJ casual) (NNS days)))))))) (. .)))