De or het zandhelling?

The correct Dutch article is:

de zandhelling

Rule Words ending in -ing: almost always de. See the rule

How to use zandhelling

the zandhellingde zandhelling
this zandhellingdeze zandhelling
that zandhellingdie zandhelling
our zandhellingonze zandhelling
your zandhellingjouw zandhelling
every zandhellingelke zandhelling
which zandhelling?welke zandhelling?
a big zandhelling / the big zandhellingeen grote zandhelling, de grote zandhelling