De or het reservepolitie?

The correct Dutch article is:

de reservepolitie

Rule Words ending in -tie and -sie: almost always de. See the rule

How to use reservepolitie

the reservepolitiede reservepolitie
this reservepolitiedeze reservepolitie
that reservepolitiedie reservepolitie
our reservepolitieonze reservepolitie
your reservepolitiejouw reservepolitie
every reservepolitieelke reservepolitie
which reservepolitie?welke reservepolitie?
a big reservepolitie / the big reservepolitieeen grote reservepolitie, de grote reservepolitie