De or het watersamenstelling?

The correct Dutch article is:

de watersamenstelling

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

How to use watersamenstelling

the watersamenstellingde watersamenstelling
this watersamenstellingdeze watersamenstelling
that watersamenstellingdie watersamenstelling
our watersamenstellingonze watersamenstelling
your watersamenstellingjouw watersamenstelling
every watersamenstellingelke watersamenstelling
which watersamenstelling?welke watersamenstelling?
a big watersamenstelling / the big watersamenstellingeen grote watersamenstelling, de grote watersamenstelling