A、Because it is clean. B、Because it tastes delicious. C、Because it saves time. D、Because it is nutritious. C选项和原因有关。从In the U. S

Many changes are taking place in food style in the U. S. America is traditionally famous for its very solid and unchanging diet of meat and potatoes. Now we have many different alternatives to choose from, various ethnic food, health food and fast food in addition to the traditional home-cooked meal.
    Ethnic restaurants and supermarkets are commonplace in the U. S. because the U.S. is a country of immigrants. There is an immense variety. Any large American city is filled with restaurants serving international cooking. Many cities even have ethnic sections: Chinatown, Little Italy or Germantown. With this vast ethnic choice, we can enjoy food from all over the world. This is a pleasant thought for those who come here to travel or to work. They can usually find their native specialties.
    Health food gained popularity when people began to think more seriously about their physical well-being. The very term health food is ironic because it implies that there is also unhealth food. Health food is fresh, natural and unprocessed food. It does not contain preservatives to make it last longer or chemical to make it taste or look better. Most health food enthusiasts are vegetarians. They eat no meat. They prefer to get their essential protein from other sources, such as beans, cheese and eggs.     Fast food restaurants are now expanding rapidly all over the country. In the U.S. speed is very important. People usually have a short lunch break or they just do not want to waste their time eating. Fast food restaurants are places which take care of hundreds of people in a short time. There is usually very little waiting and the food is always cheap. Some examples are hamburger and pizza places.