A、To reduce the costs of waste. B、To keep the airports clean and tidy. C、To shorten the time of dealing with trash. D、To remind

Experts in the food industry are thinking a lot about trash these days. Restaurants, colleges, hospitals and other institutions are trying to lower the costs of waste in new ways. Some are tracking their trash with software systems, making food in smaller amounts or trying to cut down on trash-hauling costs. Roughly 30% of food in the United States goes to waste, costing some $ 48 billion annually. A recent study estimated that 40 to 50 percent of food in the United States was wasted. Freshman students at Virginia Tech were surprised this year when they entered two of the campus’s biggest dining halls to find there were no cafeteria trays. One student said without trays, students took less food and didn’t eat more than they should. Getting rid of trays has cut food waste by 38% at the cafeterias. That same phenomenon often happens at Oregon’s Portland International Airport. Busy travelers often throw half-eaten meals into trash cans and the airport must pay the city to haul the waste away. Now the airport is carrying out a program to install food-only trash cans. The food waste is collected and given to the city to use in agriculture. Besides being environmentally friendly, the changes may save the airport money. It costs about $ 82 to have one ton of trash hauled, but food waste costs only about $ 48 a ton to haul. Cutting back on the waste can require spending money on software and training. There are software systems that track food being thrown out. Steve Peterson is the head chef at the MGM Grand Hotel. He was surprised when he installed the software system and saw the value of food that was going out of the back door. To cut costs, Peterson decided to reduce serving sizes.
19.  What is the main aim of people paying attention to food waste?      
20.  Why do the dining halls in Virginia Tech have no trays?      
21.  What’s the purpose of installing food-only trash cans at the airport?      
22.  How can the software system help reduce the food waste?