⇒ We should protect the enviroment by using 3R, using public transports, saving energy,...

Lời giải:

To have a small carbon footprint, we should turn off the lights, fans, televisions and computers when you don't use them. We should use public transports when travelling in long distances and walk or ride a bike when travelling in short distances. We should use biogas for cooking and use solar energy. Follow these ways, we can have a small carbon footprint.