The American idea of customer service is to make each customer the center of attention. People going shopping in America can expect to be treated with respect from the very beginning. When customers get to the store, they are treated as honored guests. Customers don't usually find store clerks sitting around watching TV or playing cards. Instead, the clerks greet them warmly and offer to help them find what they want. In most stores, the signs that label each department make shopping a breeze (容易的事情). Customers usually don't have to ask how much items cost, since prices are clearly marked.
When customers are ready to check out, they find the nearest and shortest checkout lane. But as Murphy's Law would have it, whichever lane they get in, all the other lanes will move faster. Good stores open new checkout lanes when the lanes get too long. Some even Offer express lanes for customers with 10 items or less. After they pay for their purchases, customers receive a smile and a warm "thank you" from the clerk. Many stores even allow customers to take their shopping carts out to the parking lot. In that way, they don't have to carry heavy bags out to the car.
In America, customer service continues long after the sale. Many products come with a money-back guarantee, ff there is a problem with the product, customers can take it back. The customer service representative will often allow them to exchange the item or return it for a full refund.
From the passage we know in America the principle of customer service is ______.

A. to be fast and convenient
B. to make customer the center of attention
C. to be the first in the world
D. to make the customer feel at home