A、They don’t like eating meat. B、They want to keep in shape. C、They think it is unsafe to eat meat. D、They think it is unethical

　　Every second in the US alone, more than 250 animals are slaughtered for food, adding up to more than eight billion animals each year. (22) Reducing the amount of meat in one’s diet is nutritionally, environmentally and ethically beneficial.  People who eat meat usually have weaker immune systems compared to those vegetarians. (23) Furthermore, meat-eaters are at a higher risk for diseases including cancer, and they are more likely to die from these diseases. Critics say that a meatless diet does not provide enough nutrients, especially protein and iron. Actually, protein is found in almost every food, and iron appears in many vegetables. Getting enough nutrients in a meat-reduced diet should not be difficult. Diet including more fruits and vegetables will only make people healthier. Some skeptics (持怀疑态度的人) believe that there will be a shortage of food if animals are not eaten. In fact, the opposite is true. (24) More than 80% of the corn and 95% of the oats grown in the US are fed to livestock. The world’s cattle alone consume enough food to equal the calorie needs of 8. 7 billion people, more than the entire human population. (24) One half of the water used in the US also goes to livestock. If people eat less meat and more plants, the amount of available food will increase. (25) Many people become vegetarians because they feel that eating animals is unethical. Ninety percent of these animals are raised in confinement. Chicken and other birds have only about half a square foot of space each, and since they are raised so close together, a hot blade is used to cut off their beaks to prevent them from pecking each other to death.
　　22. What’s the passage mainly about?
　　23. Which is one of the reasons why we should eat less meat?
　　24. Why does the speaker say eating less meat is environmentally beneficial?
　　25. Why do many people become vegetarians according to the speaker?