Passage Three Americans are well known for the strange diets th

Passage Three Americans are well known for the strange diets they always seem to be following．It seems that Americans like to diet almost as much as they like to eat．New types of diet plans are always coming out．Usually,though,they don't stay popular for long． There are many diets on the market．It is often difficult to know which ones really work．It's also hard to believe how fast a dieter is supposed to shed pounds．A lot has been written about dieting．And some interesting facts about diets and foods have been discovered． For example,did you know that the more celery you eat,the more weight you will lose?Celery has“negative”calories．The body burns up more calories digesting a piece of celery than there are in the celery stick itself． Dieters?shun?potatoes because they think they are fattening．But they aren't．A potato has about the same number of calories as an apple．To gain a single pound,you would have to eat eleven pounds of potatoes! Some dieters even worry about getting fat from licking postage stamps．But they have nothing to worry about．The glue on an average stamp has only about one-tenth of a calorie．Maybe a diet of post-age stamps would be popular? This passage is all about______
A、vegetables
B、fads
C、Americans
D、dieting
【正确答案】：D
【题目解析】：文章主要围绕“美国人”和他们的“奇怪饮食”习惯进行描述。从首句“Americans are well known for the strange diets they always seem to be following”可以看出，文章的主题与“美国人的饮食”有关。接下来，文章详细描述了各种新的饮食计划、市场上的各种饮食方法、以及关于食物和饮食的一些有趣事实。这些描述都紧密围绕“饮食”这一主题。 观察选项： A. vegetables（蔬菜）：虽然文章中提到了芹菜和土豆，但这只是作为支持主题的例证，文章并非专门讨论蔬菜。 B. fads（时尚，一时的风尚）：文章没有专门讨论时尚或风尚。 C. Americans（美国人）：虽然文章以“美国人”为引子，但主要是讨论他们的饮食习惯，而不是美国人的其他方面。 D. dieting（饮食）：这个选项准确地概括了文章的主要内容，即关于美国人的饮食习惯和饮食计划。 因此，正确答案是D，即这篇文章主要是关于“饮食”的。