Which of the following statements is NOT a correct description of emissions trading. a) Emissions trading have not had as much impact as expected. This is in part due to the difficulty of putting a price of carbon, and the issue of using a price that is too low to have any effect. b) Emissions trading was introduced through the Kyoto Protocol as a mandatory part of the agreements. Nations that signed the protocol were expected to set up a national emissions trading system within a five-year period. c) Currently, the largest emissions trading system exists in the European Union. The system covers about 45% of emissions in the EU. d) Emissions trading is based on the idea that actors should pay for their carbon emissions. Putting a price on carbon will, according to economic theory, encourage actors to reduce their emissions