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I. Underline the silent letters in the words below. Doubt                foreigner                  awful                        Christmas Muscle              yacht                        vegetable                  pneumonia Wednesday       history                      design                       calm science              listen                          honest                      subtle plumber              psychology              wreck                        answer evening             handkerchief             exhaust                    receipt knee                 interest                       thought                     although island                neighbor                   walk                               honest ocean               vehicle                      literature                        ghost cupboard          autumn                    sword                           castle

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Read the passage and answer the questions. We use many different energy sources to do work for us. Energy sources are classified into two groups - renewable and nonrenewable. Non-renewable energy sources are those that take millions of years to form and will run out some day. It is energy that comes from fossil fuels such as coal, crude oil, and natural gas. Fossil fuels are mainly made up of carbon and were formed millions of years ago. The chemical reaction which takes place when we burn fossil fuels releases carbon compounds such as carbon monoxide and carbon dioxide into the air. Carbon dioxide is one of the green house gases which is contributing to global warming and air pollution. On the other hand, renewable energy sources will never run out, are better for the environment and do not cause pollution. Renewable energy is often called green energy because it is a natural energy, always available and does not have to be formed like nonrenewable energy. The green energy is always there. For example, the Sun consistently shines, water is abundant, and the winds blow throughout the year. The five types include solar, energy from the Sun; geothermal, energy from heat within the Earth; hydroelectric, energy from moving water; biomass, energy from dead plants and microorganisms and finally, energy from the wind. 1. What are fossil fuels? 2. When were fossil fuels formed? 3. Do carbon dioxide emissions causes climate change on Earth? 4. How many types of renewable energy sources are there? What are they? 5. Are renewable sources bad for the environment? 6. Why is renewable energy called green energy?

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