A、Eggs and their recipes. B、Eggs and their substitutes. C、Misconceptions about eggs. D、The nutritional value of eggs. B录音全篇主要讲的是

Though they are an extensive supplier of vitamin, minerals and high-quality protein, eggs also contain a high level of blood cholesterol, one of the major causes of heart disease.
    One egg yolk, in fact, contains a little more than two-thirds of the cholesterol the body needs daily. This knowledge has caused egg sales to drop in recent years, which in turn has brought about the development of several alternatives to eating regular egg.
    One alternative is to eat substitute eggs. These egg substitutes are not really eggs. But they look somewhat like eggs when they are cooked. They have the advantage of having lower cholesterol rate, and they can be scrambled or used in baking. One disadvantage, however, is that they are not good for frying or boiling. A second alternative to regular eggs is a new type of egg, sometimes called “designer” eggs. These eggs are produced by hens that are fed low-fat diet including such ingredients as corn, flax, and rice bran. In spite of their diet, however, these hens produce eggs that contain the same amount of cholesterol as regular eggs. Yet, the producers of these eggs claim that eating their eggs will not raise the blood cholesterol all in human.
Questions:
21. What is good about the eggs?
22. What happened when people came to know the high level of cholesterol in eggs?
23. What has been one of the approaches to the problem of cholesterol?
24. What makes these designer eggs different from the regular ones?
25. What is the main idea of the talk?