An international group of coffee experts has considered Ethiopia's coffee as the best in the world. Coffee is a top export ( ) of the country. But at home, it is seen as national pride. Ethiopians feel good about their coffee, and enjoying a drink with friends is a long tradition. Some people say the climate produces quality beans. Morton Wennersgarrd is a coffee importer. He said,"Ethiopia has different ancient types of coffee. They are planted in places with perfect soil, perfect altitude ( ), and climates that are really suitable for coffee processing." Finding the best quality beans is often an issue of taste. The process is known as cupping -- tasting and comparing coffee from different roasted beans, grading and then pricing them. But before international experts come to taste, coffee beans are studied in small coffee laboratories. Helen Assefa, a lab technician, describes the process, "When the coffee comes to the lab, we assess ( ) its quality first by recording the details. Then we weigh the moisture   level and we examine the beans for analysis. After that we grind ( ) the coffee beans and taste the samples. At the end we check for defective   beans." Mubarik Abaoli is a lab worker. He says that testing is a very difficult and long process. "We select out the defects by hand. And we select out the defect according to the defect types." Ethiopia has got a lot of money by exporting coffee to more than 120 countries. The country has an export revenue ( ) of more than $840 million a year. But not all the best coffee leaves Ethiopia. Forty percent of the coffee grown in the country stays there. It remains an important part of everyday life at work, at home and at ceremonies. What is the main purpose of the passage?
To advertise the coffee in Ethiopia. To comment on coffee experts' work. To introduce the best coffee in the world. To recommend tourists activities in Ethiopia.