[B] It is a unit under the Kyoto Protocol representing a reduction of greenhouse gases under the Joint Implementation mechanism
[C] It is a administrative approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollution
[D] All of above are correct
Please note that Carbon footprint is amount of carbon dioxide released in the atmosphere everyday by an electronic gadget / organization. The quantity of all green house gases put together required to maintain the temperature of the environment at a fixed level of 30 degree C at nodal points in the country is also referred to as carbon foot print. The second statement a unit under the Kyoto Protocol representing a reduction of greenhouse gases under the Joint Implementation mechanism is the definition of Emission Reduction Unit, while statement C is emission trading.