fixed coupling造句

In the UK, it is normal to randomly assign fixed couples, and then keep those couples fixed throughout the competition ( for example, if there are multiple rounds ).
These can be performed by fixed couples or in the more sociable " progressive " manner, with the lady moving to the next gentleman in the ring at or near the end of each repetition of the steps.
But then the writer felt if the show had an odd number ( two guys and three girls or four guys and two girls ), it would add more dynamic and improbability to the equation : there won't be any fixed couples.
It's difficult to find fixed coupling in a sentence. 用fixed coupling造句挺难的