What is a real life situation involving permuations?

Permutation is a way, especially one of several possible variations, in which a set or number of things can be ordered or arranged.
In Mathematics, it is the action of changing the arrangement, especially the linear order, of a set of items.We can use it when:
1. arranging books at the library2. setting schedules3. organizing lists by priority (see images below)

It's most likely choice a, it makes the most sense in my opinion.