What would happen if that airline or road or checkout counter became especially popular, or you wanted to use them during a particularly busy time?

Help bag your own groceries at the checkout counter.

Imagine that you were only allowed to fly on one airline, or take a single route to work, or use one designated checkout counter at the grocery store.

The next day, she tried to buy three cans of dog food. Again the cashier demanded proof that she had a dog, because older people sometimes eat dog food.

as he stepped up to the checkout counter, he saw that his total was 127.5, how can that be? i am only purchasing a few things.