De or het randbemerking?

The correct Dutch article is:

de randbemerking

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

How to use randbemerking

the randbemerkingde randbemerking
this randbemerkingdeze randbemerking
that randbemerkingdie randbemerking
our randbemerkingonze randbemerking
your randbemerkingjouw randbemerking
every randbemerkingelke randbemerking
which randbemerking?welke randbemerking?
a big randbemerking / the big randbemerkingeen grote randbemerking, de grote randbemerking