What is the answer to this abstract reasoning puzzle?

https://i.imgur.com/oEPk87m.jpeg

In New Zealand, in order to get into the Defence Force, we have something called the NZDF Aptitude test. This was one of the questions in a practice test. No answers were provided.

Me and my student were stumped. I asked my football team (shout out HSOB Christchurch) and we couldn't come up with a satisfactory answer either. AI also came up short.