IX. Read the following passage carefully, and then answer the questions. We send young people of different nationalities on expeditions around the world. Our volunteers get the chance to work with local people to learn about different cultures. There are ten expeditions every year. Each expedition lasts for ten weeks and takes 150 volunteers. They go to countries such as Chile, Namibia, Mongolia and Viet Nam. Some of our volunteers work with local people to provide facilities, for example, building schools. Others work in national parks or help scientists to do environmental research. These adventurous, young people come from all over the world. To become a volunteer, you have to be between 17 and 25; you have to speak some English and you also have to be enthusiastic, flexible and hard-working members of a team. 76. Who goes on the expeditions? 77. How many .expeditions are there every year? 78. How long does each expedition last? 79. What do the volunteers help scientists? 80. Which language must we know to become a volunteer?