79. A carbon footprint is the amount of greenhouse gases, primarily carbon dioxide,released into the atmosphere by a particular human activity. Which of the followingactivities has the highest carbon footprint？
(A) use air conditioner overnight (need 20 kwh electricity)
(B) eat beef noodle for lunch (eat 0.25kg beef)
(C) ride scooter for 50 km (spent 3Liter gasoline)
(D) ride U-bike to school for a month