Parts of speech / word formation

I need you to understand the _____________ that this job requires.

I have been ___________ researching about this topic for my thesis.

I will stay in this business as long as it is _________.

We have the __________ that he's steling money from from the register.

In medieval times, princes and princesses got married to __________ relations between kingdoms.

I just can ___________ with that kind of people, I just hate what they do.

He won't change his whole _________ system just because you say so.