Read the article and select the best answer. Article: This winter, the air quality over the north China plain was so bad that it was actually off the standard scale. The air pollution reached levels that the World Health Organization describes as dangerous. On Thursday, heavy smog blanketed most of northern and eastern China again. It is reasonable to ask why the air pollution is so bad this winter. Weather conditions and topographic factors have been given as reasons, but, although contributing factors, these are not to blame. The worsening air pollution is linked to an energy mix that relies heavily on coal and to motor vehicle emissions . But despite the astonishing growth of motor vehicles in our cities, it is the burning of coal that is the biggest cause of air pollution. More than half of the country's power plants are located in the eastern region and China's coal consumption has more than doubled in the past decade, reaching 3.8 billion tons last year, accounting for almost half the world's total coal consumption. And with coal occupying nearly 70 percent of the country's primary energy consumption, it has become critical to reduce the use of coal if we are to solve the nation's overall air pollution problem. In the face of the poisonous air recently, one citizen said, "we have nothing but hot air to purify the skies". In fact, the government plans to have 350 billion yuan ($55.67 billion) investment in improving coal-fired facilities and limiting the use of yellow-label cars that do not meet the Euro I emissions standard and so on. However, it would be far more effective to reduce emissions at the source, which means that the biggest challenge currently facing government departments is saying "no" to the country's air polluting offenders. According to the Joint Prevention and Control Plan on Air Pollution in Key Regions released recently by the State Council, the amount of coal the nation consumes is set to rise by 30 percent during the period of the 12th Five-Year Plan. This is not going to let anyone breathe easier. This highlights a key problem when... Question: According to the writer, which of the following is the key to solving the air pollution problem? Options: A: Giving priority to economic development in policymaking. B: Making environment-friendly policies and carrying them out effectively. C: Increasing investment in the construction of coal-fired facilities. D: Limiting the use of cars not meeting the required emission standard
A:
B