SGMC polygons matching unit identifier CAgrpCA?;0

The shapefile could not be created.
pgsql2shp -f output/CAgrpCA?_0 -h igscsahcppg02 -u emrt -P usgs -g wgs84_geom mrdata "select gid,state,unit_link,ref_id,generalize,src_url,'https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit='||unit_link as url,wgs84_geom from sgmc2.geol_poly where unit_link='CAgrpCA?;0'"
Initializing...
Done (postgis major version: 2).
Output shape: Polygon
Dumping: X [1 rows].
zip -m CAgrpCA?_0.zip CAgrpCA?_0.*
  adding: CAgrpCA?_0.dbf (deflated 53%)
  adding: CAgrpCA?_0.prj (deflated 40%)
  adding: CAgrpCA?_0.shp (deflated 24%)
  adding: CAgrpCA?_0.shx (deflated 45%)