听力原文： Man: And now with today's consumer report, here's Consumer Affairs Editor Alice Dunn to tell us about the nutritional value of bread. Woman: Thank you, Chris. You know, today—with so many Americans counting calories and wanting to eat more natural foods—there are many new kinds of bread on supermarket shelves, high fiber bread, wheat germ bread, low calorie bread, to name only a few. Well, despite the variety, the principal ingredients of bread have remained the same. flour, water, and yeast. There may be a few other things added as food for the yeast to help it develop or as agents to assist the baking process, but these additives appear in minute quantities and have little effect on calories or nutrition. Man: Well, what about the differences between white bread and whole grain bread, Alice? Is whole grain bread really superior nutritionally? Woman: Both have their advantages, Chris. Whole grain bread does have more fibers of course, and the bulk which the fiber provides can be useful in digestion. White bread has a finer texture. The reason that so many people feel white bread is nutritionally lacking is the bleaching process. Bleaching, which gives bread its distinctive white color, does remove many nutrients. But what many people are unaware of is that these nutrients are added back into the bread after the bleaching process. And this re-adding process has a distinct advantage for some people. One nutrient that is re-added, iron, is unbounded in white bread whereas the iron which is retained in its natural state in whole grain bread is bonded to other chemical constituents. Studies have shown that some people have difficulty absorbing the bonded iron but can readily absorb the unbounded iron in bleached white bread. Probably the soundest advice for most people is to eat some of both types of bread. And now here's a story which makes the good old days seem that much further in the past. Do you still remember the nickel candy bar that you used to buy on the way home from school when you were a child? Well, after successive increases to 10, 15, and 20 cents, the old nickel candy bar is now going to cost you a quarter. Candy manufacturers report that the bars will be larger. But, whereas the price is increasing 25%, the average weight increase for a bar is only 14%. Man：Thank you, Alice. We'll have more news after we return from a commercial break. 19.According to the report, what are the three main ingredients found in bread? 20.What advantage does unbounded iron offer? 21.Which of the following statements about bread is true? 22.What gives white bread its distinctive color? (39)