While the supermarkets have been moving in the direction of self-service in exchange for lower prices, smaller enterprises have sprung up to supply home service to those who want it, especially to the many people who now live in rural or suburban areas. Our country district is visited regularly by a grocer, a greengrocer, several bakers, a dispenser of frozen foods and there ice cream men, not to mention the occasional salesman of brushes, insurance, magazines or cars, and that absolutely indispensable country institution, the rural letter carrier.
The accent on service suggests an attempt to blend (混合) the two conflicting foes in the national character-the hard-headed (固执的) drive for business success and the soft religiously inspired urge to serve others. As the recipients of such services we in turn find ourselves wanting to support them all, for if they are taking the trouble to serve us it seems only fair that they should be helped to succeed.
Which of following best describes the main idea of the passage？ ______.

Americans are the best served in the world
B. The production of services in America has risen from 25% to 35%
C. Supermarkets have moved in the right direction of self-service
D. Service as an ideal of American people has entered into many fields of lives of Americans