In the past , people shopped for fruits, vegetables, bread and meat at small food stores and at open markets. Before there were _ , it was difficult to keep food fresh for a long time, so people shopped almost every day. Life today is very different from the past. Refrigerators keep food fresh, so people don't have to shop every day. People also have very busy lives. They have time to shop for food only once or twice a week. People shop for food in different kinds of places--in small stores, at large supermarkets and sometimes at wholesale  stores that sell food and other things at very low prices. Some people even shop on the Internet. They order food online, and the company sends it to their home. And in many places around the world, people still shop at open markets. So people in different places like to shop for food in different ways. What's the main idea of this passage?
The different ways to shop food in the past and now. The different stores to sell food in the past and now. All kinds of foods at very low prices on the Internet Keeping food fresh for a long time in the refrigerators.