Order the words to make sentences (Sắp xếp các từ để tạo thành câu) 1. or we / stop using fossil fuels / we should / to breathe will have no fresh air 2. we ought / using coal / pollutes the air / to stop / because it 3. an effective source / but / nuclear power is / very dangerous / of energy / it is 4. look for / we will have / we should / alternative sources of energy / and / a better environment 5. an effective source / although / nuclear power is / very dangerous / of energy / it is