What is the text mainly about? A. What appliances to buy to save energy. B. What a carbon footprint means in our life. C. How to identify different carbon footprints. D. How to make eco-friendly lifestyle choices.What do we know about the secondary carbon footprint? A. It is related to our consumption of fuels. B. It is made when we are buying the products. C. It is less harmful than the primary carbon footprint. D. It is counted as ours though not directly made by us.Which of the following helps reduce our carbon footprint according to the author? A. Using second-hand textbooks. B. Using old and expensive cars. C. Buying new but cheap clothes. D. Buying new wooden furniture.7.“The footprint” underlined in the last sentence refers to the CO2 produced in .A. using the product B. recycling the productC. making the product D. transporting the product