Use the following options to set what happens when you select Curves > Duplicate Surface Curves.
Creates the duplicated curve as a child of the surface from which it was created. This affects transformations applied to the curve (or surface).
For example, duplicate a cylinder isoparm, move the middle CV of the resulting curve in X, then rotate the cylinder 90 degrees about Z. If this option is turned on, the center CV of the curve is moved in X. If off, the center CV is moved in Y.
Lets you duplicate all isoparms of an object in the U, V, or U and V directions. This option works only when the entire surface is selected.
U specifies all isoparms in the U direction. V specifies all isoparms in the V direction. Both specifies both U and V directions (all isoparms).