A、They behave as if their memories have failed totally. B、They grab whatever they think is a good bargain. C、They become excited

Since I started working part-time at a grocery store, I have learned that a customer is more than someone who buys something. To me, a customer is a person whose memory fails entirely once he or she starts to push a shopping cart. One of the first things customers forget is how to count. There’s no other way to explain how so many people get in their express line, which is clearly marked 15 items or less, with 20, 25 or even a cart load of items. Customers also forget why they came to the store in the first place. Just as I finish ringing up an order, a customer will say, "Oops, I forgot to pick up a fresh loaf of bread. I hope you don’t mind waiting while I go get it." Five minutes later, he’s back with the bread, a bottle of milk, and three rolls of paper towels. Strange is it seems customers also seem to forget that they have to pay for their groceries. Instead of writing a check or looking for a credit card while I am ringing up the groceries, my customer will wait until I announce the total. Then, in surprise, she says, "Oh no, what did I do with my check book?" After 5 minutes of digging through her purse, she borrows my pen because she’s forgotten hers. But I have to be tolerant of customers because they pay my salary, and that’s something I can’t afford to forget.
16. What does the speaker say about customers’ entering the grocery store?
17. Which customers are supposed to be in the express line?
18. What does the speaker say some customers do when they arrive at the check-out counter?
19. What does the speaker say about his job at the end of the talk?