De or het themabrief?

The correct Dutch article is:

de themabrief

This word is not in the word lists we use to double-check answers.

How to use themabrief

the themabriefde themabrief
this themabriefdeze themabrief
that themabriefdie themabrief
our themabriefonze themabrief
your themabriefjouw themabrief
every themabriefelke themabrief
which themabrief?welke themabrief?
a big themabrief / the big themabriefeen grote themabrief, de grote themabrief