postgis - Merging multipolygon data into a polygon

I have a MultiPolygon representation of some shapes in POSTGIS, I am trying to convert them to Polygon data.

I tried, st_geometryn(r.geom, 1) but that didnt work because the way polygons are embedded I think. Just returns a partial.

Tried ST_ConcaveHull(ST_Collect(r.geom), 0.99), no luck returns nothing

Tried:

SELECT f.gid, ST_AsGeoJSON(ST_Union(f.geom)) as singlegeom FROM (SELECT gid, 
       (ST_Dump(geom)).geom As geom FROM public.nyc_boroughs ) As f GROUP BY gid" 

but getting back to Multi Polygon,

I feel like a little bit of direction could help me figure out.

Data is here http://www.sendspace.com/file/2savyw